Functional Programming

Package textrank is an implementation of Text Rank algorithm in Go with extendable features (automatic summarization, phrase extraction). It supports multithreading by goroutines. The package is under The MIT Licence. If there was a program what could rank book size text's words, phrases and sentences continuously on multiple threads and it would be opened to modifing by objects, written in a simple, secure, static language and if it would be very well documented... Now, here it is. - Find the most important phrases. - Find the most important words. - Find the most important N sentences. - Importance by phrase weights. - Importance by word occurrence. - Find the first N sentences, start from Xth sentence. - Find sentences by phrase chains ordered by position in text. - Access to the whole ranked data. - Support more languages. - Algorithm for weighting can be modified by interface implementation. - Parser can be modified by interface implementation. - Multi thread support. Find the most important phrases: This is the most basic and simplest usage of textrank. All possible pre-defined finder queries: After ranking, the graph contains a lot of valuable data. There are functions in textrank package what contains logic to retrieve those data from the graph. After ranking, the graph contains a lot of valuable data. The GetRank function allows access to the graph and every data can be retrieved from this structure. Adding text continuously: It is possibe to add more text after another texts already have been added. The Ranking function can merge these multiple texts and it can recalculate the weights and all related data. Using different algorithm to ranking text: There are two algorithm has implemented, it is possible to write custom algorithm by Algorithm interface and use it instead of defaults. Using multiple graphs: Graph ID exists because it is possible run multiple independent text ranking processes. Using different non-English languages: Engish is used by default but it is possible to add any language. To use other languages a stop word list is required what you can find here: https://github.com/stopwords-iso Asynchronous usage by goroutines: It is thread safe. Independent graphs can receive texts in the same time and can be extended by more text also in the same time.

Package glog implements logging analogous to the Google-internal C++ INFO/ERROR/V setup. It provides functions Info, Warning, Error, Fatal, plus formatting variants such as Infof. It also provides V-style logging controlled by the -v and -vmodule=file=2 flags. Basic examples: See the documentation for the V function for an explanation of these examples: Log output is buffered and written periodically using Flush. Programs should call Flush before exiting to guarantee all log output is written. By default, all log statements write to files in a temporary directory. This package provides several flags that modify this behavior. As a result, flag.Parse must be called before any logging is done.

Package log4go provides level-based and highly configurable logging. This is inspired by the logging functionality in Java. Essentially, you create a Logger object and create output filters for it. You can send whatever you want to the Logger, and it will filter that based on your settings and send it to the outputs. This way, you can put as much debug code in your program as you want, and when you're done you can filter out the mundane messages so only the important ones show up. Utility functions are provided to make life easier. Here is some example code to get started: log := log4go.NewLogger() log.AddFilter("stdout", log4go.DEBUG, log4go.NewConsoleLogWriter()) log.AddFilter("log", log4go.FINE, log4go.NewFileLogWriter("example.log", true)) log.Info("The time is now: %s", time.LocalTime().Format("15:04:05 MST 2006/01/02")) The first two lines can be combined with the utility NewDefaultLogger: log := log4go.NewDefaultLogger(log4go.DEBUG) log.AddFilter("log", log4go.FINE, log4go.NewFileLogWriter("example.log", true)) log.Info("The time is now: %s", time.LocalTime().Format("15:04:05 MST 2006/01/02")) Usage notes: Changes from 2.0: Future work: (please let me know if you think I should work on any of these particularly)

Rf refactors Go programs. Usage: Rf applies a script of refactoring commands to the package in the current directory. For example, to unexport a field in a struct by renaming it: By default, rf writes changes back to the disk. The -diff flag causes rf to print a diff of the intended changes instead. A script is a sequence of commands, one per line. Comments are introduced by # and extend to the end of the line. Commands may be broken across lines by ending all but the last with a trailing backslash (before any comment), as in: Commands that take { } blocks need not backslash-escape line breaks inside the braces, as in: Most commands take “code addresses” as arguments. Each code address identifies some code in a program. For illustration, consider this program, prog.go: The simplest code address is the name of a top-level declaration. In this program, those addresses are C, D, F, T, V, and VT. Adding .Name to an address selects a name within the earlier address, whether that's a function variable (F.who, F.msg), a struct field (T.Field), a method (T.M, T.P), or a variable's field (V.Value, V.thing, V.thing.Field, VT.Field). Another kind of code address is a Go source file, identified by a name ending in “.go”, as in “file.go”. If the file name contains a slash, as in “../dir/file.go”, the address identifies a file in the package in “../dir”. Another kind of code address is a Go package, identified by a path containing a slash but not ending in “.go”, as in “../dir” or “example.com/pkg”. A final kind of code address is a textual range in a function body or source file, identified by the syntax Ident:Range, where Ident identifies a file, function, or method and Range identifies a section of text within. The Range syntax is as used in the Acme and Sam text editors. The most common forms are the line range “N,M”, the byte range “#N,M”, and the regular expression range “/re1/,/re2/”. For example: See http://9p.io/sys/doc/sam/sam.html Table II for details on the syntax. The add command adds text to the source code. It takes as an argument the address after which the text should be added, followed by the text itself. The address may be a declaration, text range, file, or package. In all cases, the text is added immediately after the addressed location: after the declaration, after the text range, at the end of the file, or at the end of the first file in the package (considering the file names in lexical order). Examples: The cp command is like mv (see below) but doesn't delete the source and doesn't update any references. (UNIMPLEMENTED) The ex command applies rewrites based on example snippets. The arguments to ex are interpreted as Go code consisting of a sequence of imports and then a list of special “old -> new” rules. Each rule specifies that where ex finds a pattern matching old, it should replace the code with new. For example, to replace all log.Error calls with log.Panic: Declarations introduce typed pattern variables that can be used in rules. For example, to simplify certain needlessly complex uses of fmt.Sprintf: The inline command inlines uses of declared constants, functions, and types. Each use of the named declarations is replaced by the declaration's definition. If the -rm flag is given, inline removes the declarations as well. Examples: Given the declarations in the “Code addresses” section above, the first command replaces all uses of E with 2.718281828. The second replaces all uses of TAlias with T and then removes TAlias. UNIMPLEMENTED: Inlining of functions. The key command converts all struct literals for a list of types to keyed literals. Each address must identify a struct type. All literals of those struct types are updated to use the keyed form. Example: The mv command moves and renames code. When mv moves or renames old code, it also updates any references to use the new names or locations for the code. This includes updating other packages in the current module. In general, mv aims to act appropriately for any sensible combination of old and new address form. The rest of this section enumerates the specific cases that mv handles. item → renamed item Any named item can be renamed by specifying a destination that is the same code address with the final element changed. For example: In this form, the destination address must repeat the dot-separated elements leading up to the new name, changing only the final element. The repetition here distinguishes this form from other forms. var → var field A top-level variable can be moved to a new or existing field in a global variable of struct type. For example: method → func A method can be moved to a top-level function, removing the association with the receiver type. The receiver remains the first argument of the new function. For example: func → method A function can be moved to a method on the type of its first argument, assuming that type is defined in the same package where the function appears. For example: UNIMPLEMENTED. code text → new function A text range can be moved to a new function, leaving behind an appropriate call to that function. For example: code text → new method A text range can be moved to a new method, leaving behind an approriate call to that method. For example: TODO. UNIMPLEMENTED. declaration → file If the source is a top-level declaration (const, func, method, type, var) and the destination is a file, mv moves that declaration, along with any comments immediately preceding it, to the end of the destination file. For example: Naming a single item in a declaration block is taken to indicate wanting to move all items in the block. In the example from the “Code addresses” section, “mv C x.go” moves D as well. Any time a destination file must be created, mv initializes it with the header comments (those above the package declaration and any package doc) from the file the source code is being moved from. This heuristic is meant to copy header text like copyright notices. The file may be in a different package. As usual, mv updates references to the moved declaration to refer to its new location, inserting imports as needed. If the result is an import cycle, mv reports the cycle rather than attempt some kind of automatic (and likely wrong) fix. declaration → package If the source is a top-level declaration and the destination is a package, mv moves the declaration to the a file in the destination package with the same name as the one holding the source item. If the destination package does not exist, it will be created. file → file If the source and destination are both files, mv moves all code from the source file to the end of the destination file. For example: file → package If the source is a file and the destination is a package, mv moves all code from the source file to a file in the destination with the same base name. For example: package → file If the source is a package and the destination is a file, mv moves all code from the source package to the named file. For example: UNIMPLEMENTED. package → package If the source is a package and the destination is a file, mv moves all code from the source package to the destination package. from the source package to the named file. For example: UNIMPLEMENTED. many → file, many → package If the destination is a file or package, multiple sources can be listed. The mv command moves each source item in turn to the destination. The rm command removes code. Rm deletes the old code. All address forms are valid. When deleting a declaration, rm also deletes line comments immediately preceding it, up to a blank line. UNIMPLEMENTED: removal of struct fields, interface methods, text ranges. Rf is very very rough. Everything is subject to change, and it may break your programs.

Package sdk is the official AWS SDK for the Go programming language. The AWS SDK for Go provides APIs and utilities that developers can use to build Go applications that use AWS services, such as Amazon Elastic Compute Cloud (Amazon EC2) and Amazon Simple Storage Service (Amazon S3). The SDK removes the complexity of coding directly against a web service interface. It hides a lot of the lower-level plumbing, such as authentication, request retries, and error handling. The SDK also includes helpful utilities on top of the AWS APIs that add additional capabilities and functionality. For example, the Amazon S3 Download and Upload Manager will automatically split up large objects into multiple parts and transfer them concurrently. See the s3manager package documentation for more information. https://docs.aws.amazon.com/sdk-for-go/api/service/s3/s3manager/ Checkout the Getting Started Guide and API Reference Docs detailed the SDK's components and details on each AWS client the SDK supports. The Getting Started Guide provides examples and detailed description of how to get setup with the SDK. https://docs.aws.amazon.com/sdk-for-go/v1/developer-guide/welcome.html The API Reference Docs include a detailed breakdown of the SDK's components such as utilities and AWS clients. Use this as a reference of the Go types included with the SDK, such as AWS clients, API operations, and API parameters. https://docs.aws.amazon.com/sdk-for-go/api/ The SDK is composed of two main components, SDK core, and service clients. The SDK core packages are all available under the aws package at the root of the SDK. Each client for a supported AWS service is available within its own package under the service folder at the root of the SDK. aws - SDK core, provides common shared types such as Config, Logger, and utilities to make working with API parameters easier. awserr - Provides the error interface that the SDK will use for all errors that occur in the SDK's processing. This includes service API response errors as well. The Error type is made up of a code and message. Cast the SDK's returned error type to awserr.Error and call the Code method to compare returned error to specific error codes. See the package's documentation for additional values that can be extracted such as RequestId. credentials - Provides the types and built in credentials providers the SDK will use to retrieve AWS credentials to make API requests with. Nested under this folder are also additional credentials providers such as stscreds for assuming IAM roles, and ec2rolecreds for EC2 Instance roles. endpoints - Provides the AWS Regions and Endpoints metadata for the SDK. Use this to lookup AWS service endpoint information such as which services are in a region, and what regions a service is in. Constants are also provided for all region identifiers, e.g UsWest2RegionID for "us-west-2". session - Provides initial default configuration, and load configuration from external sources such as environment and shared credentials file. request - Provides the API request sending, and retry logic for the SDK. This package also includes utilities for defining your own request retryer, and configuring how the SDK processes the request. service - Clients for AWS services. All services supported by the SDK are available under this folder. The SDK includes the Go types and utilities you can use to make requests to AWS service APIs. Within the service folder at the root of the SDK you'll find a package for each AWS service the SDK supports. All service clients follows a common pattern of creation and usage. When creating a client for an AWS service you'll first need to have a Session value constructed. The Session provides shared configuration that can be shared between your service clients. When service clients are created you can pass in additional configuration via the aws.Config type to override configuration provided by in the Session to create service client instances with custom configuration. Once the service's client is created you can use it to make API requests the AWS service. These clients are safe to use concurrently. In the AWS SDK for Go, you can configure settings for service clients, such as the log level and maximum number of retries. Most settings are optional; however, for each service client, you must specify a region and your credentials. The SDK uses these values to send requests to the correct AWS region and sign requests with the correct credentials. You can specify these values as part of a session or as environment variables. See the SDK's configuration guide for more information. https://docs.aws.amazon.com/sdk-for-go/v1/developer-guide/configuring-sdk.html See the session package documentation for more information on how to use Session with the SDK. https://docs.aws.amazon.com/sdk-for-go/api/aws/session/ See the Config type in the aws package for more information on configuration options. https://docs.aws.amazon.com/sdk-for-go/api/aws/#Config When using the SDK you'll generally need your AWS credentials to authenticate with AWS services. The SDK supports multiple methods of supporting these credentials. By default the SDK will source credentials automatically from its default credential chain. See the session package for more information on this chain, and how to configure it. The common items in the credential chain are the following: Environment Credentials - Set of environment variables that are useful when sub processes are created for specific roles. Shared Credentials file (~/.aws/credentials) - This file stores your credentials based on a profile name and is useful for local development. EC2 Instance Role Credentials - Use EC2 Instance Role to assign credentials to application running on an EC2 instance. This removes the need to manage credential files in production. Credentials can be configured in code as well by setting the Config's Credentials value to a custom provider or using one of the providers included with the SDK to bypass the default credential chain and use a custom one. This is helpful when you want to instruct the SDK to only use a specific set of credentials or providers. This example creates a credential provider for assuming an IAM role, "myRoleARN" and configures the S3 service client to use that role for API requests. See the credentials package documentation for more information on credential providers included with the SDK, and how to customize the SDK's usage of credentials. https://docs.aws.amazon.com/sdk-for-go/api/aws/credentials The SDK has support for the shared configuration file (~/.aws/config). This support can be enabled by setting the environment variable, "AWS_SDK_LOAD_CONFIG=1", or enabling the feature in code when creating a Session via the Option's SharedConfigState parameter. In addition to the credentials you'll need to specify the region the SDK will use to make AWS API requests to. In the SDK you can specify the region either with an environment variable, or directly in code when a Session or service client is created. The last value specified in code wins if the region is specified multiple ways. To set the region via the environment variable set the "AWS_REGION" to the region you want to the SDK to use. Using this method to set the region will allow you to run your application in multiple regions without needing additional code in the application to select the region. The endpoints package includes constants for all regions the SDK knows. The values are all suffixed with RegionID. These values are helpful, because they reduce the need to type the region string manually. To set the region on a Session use the aws package's Config struct parameter Region to the AWS region you want the service clients created from the session to use. This is helpful when you want to create multiple service clients, and all of the clients make API requests to the same region. See the endpoints package for the AWS Regions and Endpoints metadata. https://docs.aws.amazon.com/sdk-for-go/api/aws/endpoints/ In addition to setting the region when creating a Session you can also set the region on a per service client bases. This overrides the region of a Session. This is helpful when you want to create service clients in specific regions different from the Session's region. See the Config type in the aws package for more information and additional options such as setting the Endpoint, and other service client configuration options. https://docs.aws.amazon.com/sdk-for-go/api/aws/#Config Once the client is created you can make an API request to the service. Each API method takes a input parameter, and returns the service response and an error. The SDK provides methods for making the API call in multiple ways. In this list we'll use the S3 ListObjects API as an example for the different ways of making API requests. ListObjects - Base API operation that will make the API request to the service. ListObjectsRequest - API methods suffixed with Request will construct the API request, but not send it. This is also helpful when you want to get a presigned URL for a request, and share the presigned URL instead of your application making the request directly. ListObjectsPages - Same as the base API operation, but uses a callback to automatically handle pagination of the API's response. ListObjectsWithContext - Same as base API operation, but adds support for the Context pattern. This is helpful for controlling the canceling of in flight requests. See the Go standard library context package for more information. This method also takes request package's Option functional options as the variadic argument for modifying how the request will be made, or extracting information from the raw HTTP response. ListObjectsPagesWithContext - same as ListObjectsPages, but adds support for the Context pattern. Similar to ListObjectsWithContext this method also takes the request package's Option function option types as the variadic argument. In addition to the API operations the SDK also includes several higher level methods that abstract checking for and waiting for an AWS resource to be in a desired state. In this list we'll use WaitUntilBucketExists to demonstrate the different forms of waiters. WaitUntilBucketExists. - Method to make API request to query an AWS service for a resource's state. Will return successfully when that state is accomplished. WaitUntilBucketExistsWithContext - Same as WaitUntilBucketExists, but adds support for the Context pattern. In addition these methods take request package's WaiterOptions to configure the waiter, and how underlying request will be made by the SDK. The API method will document which error codes the service might return for the operation. These errors will also be available as const strings prefixed with "ErrCode" in the service client's package. If there are no errors listed in the API's SDK documentation you'll need to consult the AWS service's API documentation for the errors that could be returned. Pagination helper methods are suffixed with "Pages", and provide the functionality needed to round trip API page requests. Pagination methods take a callback function that will be called for each page of the API's response. Waiter helper methods provide the functionality to wait for an AWS resource state. These methods abstract the logic needed to to check the state of an AWS resource, and wait until that resource is in a desired state. The waiter will block until the resource is in the state that is desired, an error occurs, or the waiter times out. If a resource times out the error code returned will be request.WaiterResourceNotReadyErrorCode. This example shows a complete working Go file which will upload a file to S3 and use the Context pattern to implement timeout logic that will cancel the request if it takes too long. This example highlights how to use sessions, create a service client, make a request, handle the error, and process the response.

Package wasmtime is a WebAssembly runtime for Go powered by Wasmtime. This package provides everything necessary to compile and execute WebAssembly modules as part of a Go program. Wasmtime is a JIT compiler written in Rust, and can be found at https://github.com/bytecodealliance/wasmtime. This package is a binding to the C API provided by Wasmtime. The API of this Go package is intended to mirror the Rust API (https://docs.rs/wasmtime) relatively closely, so if you find something is under-documented here then you may have luck consulting the Rust documentation as well. As always though feel free to file any issues at https://github.com/bytecodealliance/wasmtime-go/issues/new. It's also worth pointing out that the authors of this package up to this point primarily work in Rust, so if you've got suggestions of how to make this package more idiomatic for Go we'd love to hear your thoughts! An example of a wasm module which calculates the GCD of two numbers An example of instantiating a small wasm module which imports functionality from the host, then calling into wasm which calls back into the host.

Package cmd provides a framework that helps implementation of commands having these features: Better logging: By using github.com/cybozu-go/log package, logs can be structured in JSON or logfmt format. HTTP servers log accesses automatically. Graceful exit: The framework provides functions to manage goroutines and network server implementation that can be shutdown gracefully. Signal handlers: The framework installs SIGINT/SIGTERM signal handlers for graceful exit, and SIGUSR1 signal handler to reopen log files. Environment is the heart of the framework. It provides a base context.Context that will be canceled before program stops, and methods to manage goroutines. To use the framework easily, the framework provides an instance of Environment as the default, and functions to work with it. The most basic usage of the framework. HTTP server that stops gracefully.

Package grip provides a flexible logging package for basic Go programs. Drawing inspiration from Go and Python's standard library logging, as well as systemd's journal service, and other logging systems, Grip provides a number of very powerful logging abstractions in one high-level package. The central type of the grip package is the Journaler type, instances of which provide distinct log capturing system. For ease, following from the Go standard library, the grip package provides parallel public methods that use an internal "standard" Jouernaler instance in the grip package, which has some defaults configured and may be sufficient for many use cases. The send.Sender interface provides a way of changing the logging backend, and the send package provides a number of alternate implementations of logging systems, including: systemd's journal, logging to standard output, logging to a file, and generic syslog support. The message.Composer interface is the representation of all messages. They are implemented to provide a raw structured form as well as a string representation for more conentional logging output. Furthermore they are intended to be easy to produce, and defer more expensive processing until they're being logged, to prevent expensive operations producing messages that are below threshold. The MutiCatcher type makes it possible to collect from a group of operations and then aggregate them as a single error. Loging helpers exist for the following levels: These methods accept both strings (message content,) or types that implement the message.MessageComposer interface. Composer types make it possible to delay generating a message unless the logger is over the logging threshold. Use this to avoid expensive serialization operations for suppressed logging operations. All levels also have additional methods with `ln` and `f` appended to the end of the method name which allow Println() and Printf() style functionality. You must pass printf/println-style arguments to these methods. The Conditional logging methods take two arguments, a Boolean, and a message argument. Messages can be strings, objects that implement the MessageComposer interface, or errors. If condition boolean is true, the threshold level is met, and the message to log is not an empty string, then it logs the resolved message. Use conditional logging methods to potentially suppress log messages based on situations orthogonal to log level, with "log sometimes" or "log rarely" semantics. Combine with MessageComposers to to avoid expensive message building operations.

Package wasmtime is a WebAssembly runtime for Go powered by Wasmtime. This package provides everything necessary to compile and execute WebAssembly modules as part of a Go program. Wasmtime is a JIT compiler written in Rust, and can be found at https://github.com/bytecodealliance/wasmtime. This package is a binding to the C API provided by Wasmtime. The API of this Go package is intended to mirror the Rust API (https://docs.rs/wasmtime) relatively closely, so if you find something is under-documented here then you may have luck consulting the Rust documentation as well. As always though feel free to file any issues at https://github.com/bytecodealliance/wasmtime-go/issues/new. It's also worth pointing out that the authors of this package up to this point primarily work in Rust, so if you've got suggestions of how to make this package more idiomatic for Go we'd love to hear your thoughts! An example of a wasm module which calculates the GCD of two numbers An example of instantiating a small wasm module which imports functionality from the host, then calling into wasm which calls back into the host.

Package spanner provides a client for reading and writing to Cloud Spanner databases. See the packages under admin for clients that operate on databases and instances. Note: This package is in beta. Some backwards-incompatible changes may occur. See https://cloud.google.com/spanner/docs/getting-started/go/ for an introduction to Cloud Spanner and additional help on using this API. See https://godoc.org/cloud.google.com/go for authentication, timeouts, connection pooling and similar aspects of this package. To start working with this package, create a client that refers to the database of interest: Remember to close the client after use to free up the sessions in the session pool. Two Client methods, Apply and Single, work well for simple reads and writes. As a quick introduction, here we write a new row to the database and read it back: All the methods used above are discussed in more detail below. Every Cloud Spanner row has a unique key, composed of one or more columns. Construct keys with a literal of type Key: The keys of a Cloud Spanner table are ordered. You can specify ranges of keys using the KeyRange type: By default, a KeyRange includes its start key but not its end key. Use the Kind field to specify other boundary conditions: A KeySet represents a set of keys. A single Key or KeyRange can act as a KeySet. Use the KeySets function to build the union of several KeySets: AllKeys returns a KeySet that refers to all the keys in a table: All Cloud Spanner reads and writes occur inside transactions. There are two types of transactions, read-only and read-write. Read-only transactions cannot change the database, do not acquire locks, and may access either the current database state or states in the past. Read-write transactions can read the database before writing to it, and always apply to the most recent database state. The simplest and fastest transaction is a ReadOnlyTransaction that supports a single read operation. Use Client.Single to create such a transaction. You can chain the call to Single with a call to a Read method. When you only want one row whose key you know, use ReadRow. Provide the table name, key, and the columns you want to read: Read multiple rows with the Read method. It takes a table name, KeySet, and list of columns: Read returns a RowIterator. You can call the Do method on the iterator and pass a callback: RowIterator also follows the standard pattern for the Google Cloud Client Libraries: Always call Stop when you finish using an iterator this way, whether or not you iterate to the end. (Failing to call Stop could lead you to exhaust the database's session quota.) To read rows with an index, use ReadUsingIndex. The most general form of reading uses SQL statements. Construct a Statement with NewStatement, setting any parameters using the Statement's Params map: You can also construct a Statement directly with a struct literal, providing your own map of parameters. Use the Query method to run the statement and obtain an iterator: Once you have a Row, via an iterator or a call to ReadRow, you can extract column values in several ways. Pass in a pointer to a Go variable of the appropriate type when you extract a value. You can extract by column position or name: You can extract all the columns at once: Or you can define a Go struct that corresponds to your columns, and extract into that: For Cloud Spanner columns that may contain NULL, use one of the NullXXX types, like NullString: To perform more than one read in a transaction, use ReadOnlyTransaction: You must call Close when you are done with the transaction. Cloud Spanner read-only transactions conceptually perform all their reads at a single moment in time, called the transaction's read timestamp. Once a read has started, you can call ReadOnlyTransaction's Timestamp method to obtain the read timestamp. By default, a transaction will pick the most recent time (a time where all previously committed transactions are visible) for its reads. This provides the freshest data, but may involve some delay. You can often get a quicker response if you are willing to tolerate "stale" data. You can control the read timestamp selected by a transaction by calling the WithTimestampBound method on the transaction before using it. For example, to perform a query on data that is at most one minute stale, use See the documentation of TimestampBound for more details. To write values to a Cloud Spanner database, construct a Mutation. The spanner package has functions for inserting, updating and deleting rows. Except for the Delete methods, which take a Key or KeyRange, each mutation-building function comes in three varieties. One takes lists of columns and values along with the table name: One takes a map from column names to values: And the third accepts a struct value, and determines the columns from the struct field names: To apply a list of mutations to the database, use Apply: If you need to read before writing in a single transaction, use a ReadWriteTransaction. ReadWriteTransactions may abort and need to be retried. You pass in a function to ReadWriteTransaction, and the client will handle the retries automatically. Use the transaction's BufferWrite method to buffer mutations, which will all be executed at the end of the transaction: Spanner supports DML statements like INSERT, UPDATE and DELETE. Use ReadWriteTransaction.Update to run DML statements. It returns the number of rows affected. (You can call use ReadWriteTransaction.Query with a DML statement. The first call to Next on the resulting RowIterator will return iterator.Done, and the RowCount field of the iterator will hold the number of affected rows.) For large databases, it may be more efficient to partition the DML statement. Use client.PartitionedUpdate to run a DML statement in this way. Not all DML statements can be partitioned. This client has been instrumented to use OpenCensus tracing (http://opencensus.io). To enable tracing, see "Enabling Tracing for a Program" at https://godoc.org/go.opencensus.io/trace. OpenCensus tracing requires Go 1.8 or higher.

Golex is a lex/flex like (not fully POSIX lex compatible) utility. It renders .l formated data (https://westes.github.io/flex/manual/Format.html#Format) to Go source code. The .l data can come from a file named in a command line argument. If no non-opt args are given, golex reads stdin. Options: To get the latest golex version: Please see http://godoc.org/modernc.org/golex/lex. 2014-11-18: Golex now supports %yym - a hook which can be used to mark an accepting state. Consider for example this .l file: Execution and output: 2014-11-15: Golex's output is now gofmt'ed, if possible. Missing/differing functionality of the current renderer (compared to flex): Further limitations on the .l source are listed in the cznic/lex package godocs. A simple golex program example (make example1 && ./example1):

Package gitfs is a complete solution for static files in Go code. When Go code uses non-Go files, they are not packaged into the binary. The common approach to the problem, as implemented by (go-bindata) https://github.com/kevinburke/go-bindata is to convert all the required static files into Go code, which eventually compiled into the binary. This library takes a different approach, in which the static files are not required to be "binary-packed", and even no required to be in the same repository as the Go code. This package enables loading static content from a remote git repository, or packing it to the binary if desired or loaded from local path for development process. The transition from remote repository to binary packed content, to local content is completely smooth. *The API is simple and minimalistic*. The `New` method returns a (sub)tree of a Git repository, represented by the standard `http.FileSystem` interface. This object enables anything that is possible to do with a regular filesystem, such as opening a file or listing a directory. Additionally, the ./fsutil package provides enhancements over the `http.FileSystem` object (They can work with any object that implements the interface) such as loading Go templates in the standard way, walking over the filesystem, and applying glob patterns on a filesystem. Supported features: * Loading of specific version/tag/branch. * For debug purposes, the files can be loaded from local path instead of the remote repository. * Files are loaded lazily by default or they can be preloaded if required. * Files can be packed to the Go binary using a command line tool. * This project is using the standard `http.FileSystem` interface. * In ./fsutil there are some general useful tools around the `http.FileSystem` interace. To create a filesystem using the `New` function, provide the Git project with the pattern: `github.com/<owner>/<repo>(/<path>)?(@<ref>)?`. If no `path` is specified, the root of the project will be used. `ref` can be any git branch using `heads/<branch name>` or any git tag using `tags/<tag>`. If the tag is of Semver format, the `tags/` prefix is not required. If no `ref` is specified, the default branch will be used. In the following example, the repository `github.com/x/y` at tag v1.2.3 and internal path "static" is loaded: The variable `fs` implements the `http.FileSystem` interface. Reading a file from the repository can be done using the `Open` method. This function accepts a path, relative to the root of the defined filesystem. The `fs` variable can be used in anything that accept the standard interface. For example, it can be used for serving static content using the standard library: When used with private github repository, the Github API calls should be instrumented with the appropriate credentials. The credentials can be passed by providing an HTTP client. For example, to use a Github Token from environnement variable `GITHUB_TOKEN`: For quick development workflows, it is easier and faster to use local static content and not remote content that was pushed to a remote repository. This is enabled by the `OptLocal` option. To use this option only in local development and not in production system, it can be used as follow: In this example, we stored the value for `OptLocal` in an environment variable. As a result, when running the program with `LOCAL_DEBUG=.` local files will be used, while running without it will result in using the remote files. (the value of the environment variable should point to any directory within the github project). Using gitfs does not mean that files are required to be remotely fetched. When binary packing of the files is needed, a command line tool can pack them for you. To get the tool run: `go get github.com/posener/gitfs/cmd/gitfs`. Running the tool is by `gitfs <patterns>`. This generates a `gitfs.go` file in the current directory that contains all the used filesystems' data. This will cause all `gitfs.New` calls to automatically use the packed data, insted of fetching the data on runtime. By default, a test will also be generated with the code. This test fails when the local files are modified without updating the binary content. Use binary-packing with `go generate`: To generate all filesystems used by a project add `//go:generate gitfs ./...` in the root of the project. To generate only a specific filesystem add `//go:generate gitfs $GOFILE` in the file it is being used. An interesting anecdote is that gitfs command is using itself for generating its own templates. Files exclusion can be done by including only specific files using a glob pattern with `OptGlob` option, using the Glob options. This will affect both local loading of files, remote loading and binary packing (may reduce binary size). For example: The ./fsutil package is a collection of useful functions that can work with any `http.FileSystem` implementation. For example, here we will use a function that loads go templates from the filesystem. With gitfs you can open a remote git repository, and load any file, including non-go files. In this example, the README.md file of a remote repository is loaded.

Package pargo provides functions and data structures for expressing parallel algorithms. While Go is primarily designed for concurrent programming, it is also usable to some extent for parallel programming, and this library provides convenience functionality to turn otherwise sequential algorithms into parallel algorithms, with the goal to improve performance. For documentation that provides a more structured overview than is possible with Godoc, see the wiki at https://github.com/exascience/pargo/wiki Pargo provides the following subpackages: pargo/parallel provides simple functions for executing series of thunks or predicates, as well as thunks, predicates, or reducers over ranges in parallel. See also https://github.com/ExaScience/pargo/wiki/TaskParallelism pargo/speculative provides speculative implementations of most of the functions from pargo/parallel. These implementations not only execute in parallel, but also attempt to terminate early as soon as the final result is known. See also https://github.com/ExaScience/pargo/wiki/TaskParallelism pargo/sequential provides sequential implementations of all functions from pargo/parallel, for testing and debugging purposes. pargo/sort provides parallel sorting algorithms. pargo/sync provides an efficient parallel map implementation. pargo/pipeline provides functions and data structures to construct and execute parallel pipelines. Pargo has been influenced to various extents by ideas from Cilk, Threading Building Blocks, and Java's java.util.concurrent and java.util.stream packages. See http://supertech.csail.mit.edu/papers/steal.pdf for some theoretical background, and the sample chapter at https://mitpress.mit.edu/books/introduction-algorithms for a more practical overview of the underlying concepts.

Package httprequest provides functionality for marshaling unmarshaling HTTP request parameters into a struct type. It also provides a way to define methods as HTTP routes using the same approach. It requires at least Go 1.7, and Go 1.9 is required if the importing program also uses golang.org/x/net/context.

Package flume is a logging package, build on top of zap. It's structured and leveled logs, like zap/logrus/etc. It adds global, runtime re-configuration of all loggers, via an internal logger registry. There are two interaction points with flume: code that generates logs, and code that configures logging output. Code which generates logs needs to create named logger instances, and call log functions on it, like Info() and Debug(). But by default, all these logs will be silently discarded. Flume does not output log entries unless explicitly told to do so. This ensures libraries can freely use flume internally, without polluting the stdout of the programs importing the library. The Logger type is a small interface. Libraries should allow replacement of their Logger instances so importers can entirely replace flume if they wish. Alternately, importers can use flume to configure the library's log output, and/or redirect it into the overall program's log stream. This package does not offer package level log functions, so you need to create a logger instance first: A common pattern is to create a single, package-wide logger, named after the package: Then, write some logs: Logs have a message, then matched pairs of key/value properties. Child loggers can be created and pre-seeded with a set of properties: Expensive log events can be avoid by explicitly checking level: Loggers can be bound to context.Context, which is convenient for carrying per-transaction loggers (pre-seeded with transaction specific context) through layers of request processing code: The standard Logger interface only supports 3 levels of log, DBG, INF, and ERR. This is inspired by this article: https://dave.cheney.net/2015/11/05/lets-talk-about-logging. However, you can create instances of DeprecatedLogger instead, which support more levels. There are several package level functions which reconfigure logging output. They control which levels are discarded, which fields are included in each log entry, and how those fields are rendered, and how the overall log entry is rendered (JSON, LTSV, colorized, etc). To configure logging settings from environment variables, call the configuration function from main(): This reads the log configuration from the environment variable "FLUME" (the default, which can be overridden). The value is JSON, e.g.: The properties of the config string: "level": ERR, INF, or DBG. The default level for all loggers. "levels": A string configuring log levels for specific loggers, overriding the default level. See note below for syntax. "development": true or false. In development mode, the defaults for the other settings change to be more suitable for developers at a terminal (colorized, multiline, human readable, etc). See note below for exact defaults. "addCaller": true or false. Adds call site information to log entries (file and line). "encoding": json, ltsv, term, or term-color. Configures how log entries are encoded in the output. "term" and "term-color" are multi-line, human-friendly formats, intended for terminal output. "encoderConfig": a JSON object which configures advanced encoding settings, like how timestamps are formatted. See docs for go.uber.org/zap/zapcore/EncoderConfig "messageKey": the label of the message property of the log entry. If empty, message is omitted. "levelKey": the label of the level property of the log entry. If empty, level is omitted. "timeKey": the label of the timestamp of the log entry. If empty, timestamp is omitted. "nameKey": the label of the logger name in the log entry. If empty, logger name is omitted. "callerKey": the label of the logger name in the log entry. If empty, logger name is omitted. "lineEnding": the end of each log output line. "levelEncoder": capital, capitalColor, color, lower, or abbr. Controls how the log entry level is rendered. "abbr" renders 3-letter abbreviations, like ERR and INF. "timeEncoder": iso8601, millis, nanos, unix, or justtime. Controls how timestamps are rendered. "millis", "nanos", and "unix" are since UNIX epoch. "unix" is in floating point seconds. "justtime" omits the date, and just prints the time in the format "15:04:05.000". "durationEncoder": string, nanos, or seconds. Controls how time.Duration values are rendered. "callerEncoder": full or short. Controls how the call site is rendered. "full" includes the entire package path, "short" only includes the last folder of the package. Defaults: These defaults are only applied if one of the configuration functions is called, like ConfigFromEnv(), ConfigString(), Configure(), or LevelsString(). Initially, all loggers are configured to discard everything, following flume's opinion that log packages should be silent unless spoken too. Ancillary to this: library packages should *not* call these functions, or configure logging levels or output in anyway. Only program entry points, like main() or test code, should configure logging. Libraries should just create loggers and log to them. Development mode: if "development"=true, the defaults for the rest of the settings change, equivalent to: The "levels" value is a list of key=value pairs, configuring the level of individual named loggers. If the key is "*", it sets the default level. If "level" and "levels" both configure the default level, "levels" wins. Examples: Most usages of flume will use its package functions. The package functions delegate to an internal instance of Factory, which a the logger registry. You can create and manage your own instance of Factory, which will be an isolated set of Loggers. tl;dr The implementation is a wrapper around zap. zap does levels, structured logs, and is very fast. zap doesn't do centralized, global configuration, so this package adds that by maintaining an internal registry of all loggers, and using the sync.atomic stuff to swap out levels and writers in a thread safe way.

Package tracelog : logcalls.go provides formatting functions. Package tracelog : logcalls.go provides formatting functions. Package tracelog implements a logging system to trace all aspect of your code. This is great for task oriented programs. Based on the Go log standard library. It provides 4 destinations with logging levels plus you can attach a file for persistent writes. A log clean process is provided to maintain disk space. There is also email support to send email alerts.

Cover is a program for analyzing the coverage profiles generated by 'go test -coverprofile=cover.out'. Cover is also used by 'go test -cover' to rewrite the source code with annotations to track which parts of each function are executed. It operates on one Go source file at a time, computing approximate basic block information by studying the source. It is thus more portable than binary-rewriting coverage tools, but also a little less capable. For instance, it does not probe inside && and || expressions, and can be mildly confused by single statements with multiple function literals. For usage information, please see: No longer maintained: For Go releases 1.5 and later, this tool lives in the standard repository. The code here is not maintained.

Package pulseaudio controls a pulseaudio server through its Dbus interface. This is a pure go binding for the pulseaudio Dbus interface. Note that you will have to enable the dbus module of your pulseaudio server. This can now be done with the LoadModule function. or by adding this line in /etc/pulse/default.pa (if system-wide daemon is used, instead edit /etc/pulse/system.pa ) Create a type that declares any methods matching the pulseaudio interface. Instead of declaring a big interface and forcing clients to provide every method they don't need, this API use a flexible interface system. The callback interface is provided by a list of single method interfaces and only those needed will have to be implemented. You can register multiple clients at any time on the same pulseaudio session. This allow you to split the callback logic of your program and have some parts (un)loadable like a client GUI. See types On... for the list of callback methods that can be used. Create a client object with some callback methods to register: Register your object and start the listening loop: There are way too many properties to have a dedicated method for each of them. First you need to get the object implementing the property you need. Then you will have to call the method matching the type of returned data for the property you want to get. See the example. Properties with the tag RW can also be set. http://www.freedesktop.org/wiki/Software/PulseAudio/Documentation/Developer/Clients/DBus/ Dbus documentation was copied to provide some useful informations here. Still valid in august 2018. Check the upstream source for updates or more informations. Create a pulse dbus service with 2 clients, listen to events, then use some properties.

package webhelp is a bunch of useful utilities for doing web programming in Go. webhelp encourages you to use the standard library for web programming, but provides some oft-needed tools to help simplify the task. webhelp tightly integrates with the new Go 1.7 Request Context support, but has backported the functionality to previous Go releases in the whcompat subpackage. Recently I wrote a long blog post about how to use webhelp: http://www.jtolds.com/writing/2017/01/writing-advanced-web-applications-with-go/

Taken from $GOROOT/src/pkg/net/http/chunked needed to write https responses to client. Package goproxy provides a customizable HTTP proxy, supporting hijacking HTTPS connection. The intent of the proxy, is to be usable with reasonable amount of traffic yet, customizable and programable. The proxy itself is simply an `net/http` handler. Typical usage is Adding a header to each request For printing the content type of all incoming responses note that we used the ProxyCtx context variable here. It contains the request and the response (Req and Resp, Resp is nil if unavailable) of this specific client interaction with the proxy. To print the content type of all responses from a certain url, we'll add a ReqCondition to the OnResponse function: We can write the condition ourselves, conditions can be set on request and on response Caution! If you give a RespCondition to the OnRequest function, you'll get a run time panic! It doesn't make sense to read the response, if you still haven't got it! Finally, we have convenience function to throw a quick response we close the body of the original repsonse, and return a new 403 response with a short message.

Package wasmtime is a WebAssembly runtime for Go powered by Wasmtime. This package provides everything necessary to compile and execute WebAssembly modules as part of a Go program. Wasmtime is a JIT compiler written in Rust, and can be found at https://github.com/bytecodealliance/wasmtime. This package is a binding to the C API provided by Wasmtime. The API of this Go package is intended to mirror the Rust API (https://docs.rs/wasmtime) relatively closely, so if you find something is under-documented here then you may have luck consulting the Rust documentation as well. As always though feel free to file any issues at https://github.com/bytecodealliance/wasmtime-go/issues/new. It's also worth pointing out that the authors of this package up to this point primarily work in Rust, so if you've got suggestions of how to make this package more idiomatic for Go we'd love to hear your thoughts! An example of a wasm module which calculates the GCD of two numbers An example of instantiating a small wasm module which imports functionality from the host, then calling into wasm which calls back into the host.

Package validator implements value validations for structs and individual fields based on tags. It can also handle Cross-Field and Cross-Struct validation for nested structs and has the ability to dive into arrays and maps of any type. see more examples https://github.com/go-playground/validator/tree/master/_examples Validator is designed to be thread-safe and used as a singleton instance. It caches information about your struct and validations, in essence only parsing your validation tags once per struct type. Using multiple instances neglects the benefit of caching. The not thread-safe functions are explicitly marked as such in the documentation. Doing things this way is actually the way the standard library does, see the file.Open method here: The authors return type "error" to avoid the issue discussed in the following, where err is always != nil: Validator only InvalidValidationError for bad validation input, nil or ValidationErrors as type error; so, in your code all you need to do is check if the error returned is not nil, and if it's not check if error is InvalidValidationError ( if necessary, most of the time it isn't ) type cast it to type ValidationErrors like so err.(validator.ValidationErrors). Custom Validation functions can be added. Example: Cross-Field Validation can be done via the following tags: If, however, some custom cross-field validation is required, it can be done using a custom validation. Why not just have cross-fields validation tags (i.e. only eqcsfield and not eqfield)? The reason is efficiency. If you want to check a field within the same struct "eqfield" only has to find the field on the same struct (1 level). But, if we used "eqcsfield" it could be multiple levels down. Example: Multiple validators on a field will process in the order defined. Example: Bad Validator definitions are not handled by the library. Example: Baked In Cross-Field validation only compares fields on the same struct. If Cross-Field + Cross-Struct validation is needed you should implement your own custom validator. Comma (",") is the default separator of validation tags. If you wish to have a comma included within the parameter (i.e. excludesall=,) you will need to use the UTF-8 hex representation 0x2C, which is replaced in the code as a comma, so the above will become excludesall=0x2C. Pipe ("|") is the 'or' validation tags deparator. If you wish to have a pipe included within the parameter i.e. excludesall=| you will need to use the UTF-8 hex representation 0x7C, which is replaced in the code as a pipe, so the above will become excludesall=0x7C Here is a list of the current built in validators: Tells the validation to skip this struct field; this is particularly handy in ignoring embedded structs from being validated. (Usage: -) This is the 'or' operator allowing multiple validators to be used and accepted. (Usage: rgb|rgba) <-- this would allow either rgb or rgba colors to be accepted. This can also be combined with 'and' for example ( Usage: omitempty,rgb|rgba) When a field that is a nested struct is encountered, and contains this flag any validation on the nested struct will be run, but none of the nested struct fields will be validated. This is useful if inside of your program you know the struct will be valid, but need to verify it has been assigned. NOTE: only "required" and "omitempty" can be used on a struct itself. Same as structonly tag except that any struct level validations will not run. Allows conditional validation, for example if a field is not set with a value (Determined by the "required" validator) then other validation such as min or max won't run, but if a value is set validation will run. Allows to skip the validation if the value is nil (same as omitempty, but only for the nil-values). This tells the validator to dive into a slice, array or map and validate that level of the slice, array or map with the validation tags that follow. Multidimensional nesting is also supported, each level you wish to dive will require another dive tag. dive has some sub-tags, 'keys' & 'endkeys', please see the Keys & EndKeys section just below. Example #1 Example #2 Keys & EndKeys These are to be used together directly after the dive tag and tells the validator that anything between 'keys' and 'endkeys' applies to the keys of a map and not the values; think of it like the 'dive' tag, but for map keys instead of values. Multidimensional nesting is also supported, each level you wish to validate will require another 'keys' and 'endkeys' tag. These tags are only valid for maps. Example #1 Example #2 This validates that the value is not the data types default zero value. For numbers ensures value is not zero. For strings ensures value is not "". For booleans ensures value is not false. For slices, maps, pointers, interfaces, channels and functions ensures the value is not nil. For structs ensures value is not the zero value when using WithRequiredStructEnabled. The field under validation must be present and not empty only if all the other specified fields are equal to the value following the specified field. For strings ensures value is not "". For slices, maps, pointers, interfaces, channels and functions ensures the value is not nil. For structs ensures value is not the zero value. Examples: The field under validation must be present and not empty unless all the other specified fields are equal to the value following the specified field. For strings ensures value is not "". For slices, maps, pointers, interfaces, channels and functions ensures the value is not nil. For structs ensures value is not the zero value. Examples: The field under validation must be present and not empty only if any of the other specified fields are present. For strings ensures value is not "". For slices, maps, pointers, interfaces, channels and functions ensures the value is not nil. For structs ensures value is not the zero value. Examples: The field under validation must be present and not empty only if all of the other specified fields are present. For strings ensures value is not "". For slices, maps, pointers, interfaces, channels and functions ensures the value is not nil. For structs ensures value is not the zero value. Example: The field under validation must be present and not empty only when any of the other specified fields are not present. For strings ensures value is not "". For slices, maps, pointers, interfaces, channels and functions ensures the value is not nil. For structs ensures value is not the zero value. Examples: The field under validation must be present and not empty only when all of the other specified fields are not present. For strings ensures value is not "". For slices, maps, pointers, interfaces, channels and functions ensures the value is not nil. For structs ensures value is not the zero value. Example: The field under validation must not be present or not empty only if all the other specified fields are equal to the value following the specified field. For strings ensures value is not "". For slices, maps, pointers, interfaces, channels and functions ensures the value is not nil. For structs ensures value is not the zero value. Examples: The field under validation must not be present or empty unless all the other specified fields are equal to the value following the specified field. For strings ensures value is not "". For slices, maps, pointers, interfaces, channels and functions ensures the value is not nil. For structs ensures value is not the zero value. Examples: This validates that the value is the default value and is almost the opposite of required. For numbers, length will ensure that the value is equal to the parameter given. For strings, it checks that the string length is exactly that number of characters. For slices, arrays, and maps, validates the number of items. Example #1 Example #2 (time.Duration) For time.Duration, len will ensure that the value is equal to the duration given in the parameter. For numbers, max will ensure that the value is less than or equal to the parameter given. For strings, it checks that the string length is at most that number of characters. For slices, arrays, and maps, validates the number of items. Example #1 Example #2 (time.Duration) For time.Duration, max will ensure that the value is less than or equal to the duration given in the parameter. For numbers, min will ensure that the value is greater or equal to the parameter given. For strings, it checks that the string length is at least that number of characters. For slices, arrays, and maps, validates the number of items. Example #1 Example #2 (time.Duration) For time.Duration, min will ensure that the value is greater than or equal to the duration given in the parameter. For strings & numbers, eq will ensure that the value is equal to the parameter given. For slices, arrays, and maps, validates the number of items. Example #1 Example #2 (time.Duration) For time.Duration, eq will ensure that the value is equal to the duration given in the parameter. For strings & numbers, ne will ensure that the value is not equal to the parameter given. For slices, arrays, and maps, validates the number of items. Example #1 Example #2 (time.Duration) For time.Duration, ne will ensure that the value is not equal to the duration given in the parameter. For strings, ints, and uints, oneof will ensure that the value is one of the values in the parameter. The parameter should be a list of values separated by whitespace. Values may be strings or numbers. To match strings with spaces in them, include the target string between single quotes. Kind of like an 'enum'. Works the same as oneof but is case insensitive and therefore only accepts strings. For numbers, this will ensure that the value is greater than the parameter given. For strings, it checks that the string length is greater than that number of characters. For slices, arrays and maps it validates the number of items. Example #1 Example #2 (time.Time) For time.Time ensures the time value is greater than time.Now.UTC(). Example #3 (time.Duration) For time.Duration, gt will ensure that the value is greater than the duration given in the parameter. Same as 'min' above. Kept both to make terminology with 'len' easier. Example #1 Example #2 (time.Time) For time.Time ensures the time value is greater than or equal to time.Now.UTC(). Example #3 (time.Duration) For time.Duration, gte will ensure that the value is greater than or equal to the duration given in the parameter. For numbers, this will ensure that the value is less than the parameter given. For strings, it checks that the string length is less than that number of characters. For slices, arrays, and maps it validates the number of items. Example #1 Example #2 (time.Time) For time.Time ensures the time value is less than time.Now.UTC(). Example #3 (time.Duration) For time.Duration, lt will ensure that the value is less than the duration given in the parameter. Same as 'max' above. Kept both to make terminology with 'len' easier. Example #1 Example #2 (time.Time) For time.Time ensures the time value is less than or equal to time.Now.UTC(). Example #3 (time.Duration) For time.Duration, lte will ensure that the value is less than or equal to the duration given in the parameter. This will validate the field value against another fields value either within a struct or passed in field. Example #1: Example #2: Field Equals Another Field (relative) This does the same as eqfield except that it validates the field provided relative to the top level struct. This will validate the field value against another fields value either within a struct or passed in field. Examples: Field Does Not Equal Another Field (relative) This does the same as nefield except that it validates the field provided relative to the top level struct. Only valid for Numbers, time.Duration and time.Time types, this will validate the field value against another fields value either within a struct or passed in field. usage examples are for validation of a Start and End date: Example #1: Example #2: This does the same as gtfield except that it validates the field provided relative to the top level struct. Only valid for Numbers, time.Duration and time.Time types, this will validate the field value against another fields value either within a struct or passed in field. usage examples are for validation of a Start and End date: Example #1: Example #2: This does the same as gtefield except that it validates the field provided relative to the top level struct. Only valid for Numbers, time.Duration and time.Time types, this will validate the field value against another fields value either within a struct or passed in field. usage examples are for validation of a Start and End date: Example #1: Example #2: This does the same as ltfield except that it validates the field provided relative to the top level struct. Only valid for Numbers, time.Duration and time.Time types, this will validate the field value against another fields value either within a struct or passed in field. usage examples are for validation of a Start and End date: Example #1: Example #2: This does the same as ltefield except that it validates the field provided relative to the top level struct. This does the same as contains except for struct fields. It should only be used with string types. See the behavior of reflect.Value.String() for behavior on other types. This does the same as excludes except for struct fields. It should only be used with string types. See the behavior of reflect.Value.String() for behavior on other types. For arrays & slices, unique will ensure that there are no duplicates. For maps, unique will ensure that there are no duplicate values. For slices of struct, unique will ensure that there are no duplicate values in a field of the struct specified via a parameter. This validates that a string value contains ASCII alpha characters only This validates that a string value contains ASCII alphanumeric characters only This validates that a string value contains unicode alpha characters only This validates that a string value contains unicode alphanumeric characters only This validates that a string value can successfully be parsed into a boolean with strconv.ParseBool This validates that a string value contains number values only. For integers or float it returns true. This validates that a string value contains a basic numeric value. basic excludes exponents etc... for integers or float it returns true. This validates that a string value contains a valid hexadecimal. This validates that a string value contains a valid hex color including hashtag (#) This validates that a string value contains only lowercase characters. An empty string is not a valid lowercase string. This validates that a string value contains only uppercase characters. An empty string is not a valid uppercase string. This validates that a string value contains a valid rgb color This validates that a string value contains a valid rgba color This validates that a string value contains a valid hsl color This validates that a string value contains a valid hsla color This validates that a string value contains a valid E.164 Phone number https://en.wikipedia.org/wiki/E.164 (ex. +1123456789) This validates that a string value contains a valid email This may not conform to all possibilities of any rfc standard, but neither does any email provider accept all possibilities. This validates that a string value is valid JSON This validates that a string value is a valid JWT This validates that a string value contains a valid file path and that the file exists on the machine. This is done using os.Stat, which is a platform independent function. This validates that a string value contains a valid file path and that the file exists on the machine and is an image. This is done using os.Stat and github.com/gabriel-vasile/mimetype This validates that a string value contains a valid file path but does not validate the existence of that file. This is done using os.Stat, which is a platform independent function. This validates that a string value contains a valid url This will accept any url the golang request uri accepts but must contain a schema for example http:// or rtmp:// This validates that a string value contains a valid uri This will accept any uri the golang request uri accepts This validates that a string value contains a valid URN according to the RFC 2141 spec. This validates that a string value contains a valid bas324 value. Although an empty string is valid base32 this will report an empty string as an error, if you wish to accept an empty string as valid you can use this with the omitempty tag. This validates that a string value contains a valid base64 value. Although an empty string is valid base64 this will report an empty string as an error, if you wish to accept an empty string as valid you can use this with the omitempty tag. This validates that a string value contains a valid base64 URL safe value according the RFC4648 spec. Although an empty string is a valid base64 URL safe value, this will report an empty string as an error, if you wish to accept an empty string as valid you can use this with the omitempty tag. This validates that a string value contains a valid base64 URL safe value, but without = padding, according the RFC4648 spec, section 3.2. Although an empty string is a valid base64 URL safe value, this will report an empty string as an error, if you wish to accept an empty string as valid you can use this with the omitempty tag. This validates that a string value contains a valid bitcoin address. The format of the string is checked to ensure it matches one of the three formats P2PKH, P2SH and performs checksum validation. Bitcoin Bech32 Address (segwit) This validates that a string value contains a valid bitcoin Bech32 address as defined by bip-0173 (https://github.com/bitcoin/bips/blob/master/bip-0173.mediawiki) Special thanks to Pieter Wuille for providing reference implementations. This validates that a string value contains a valid ethereum address. The format of the string is checked to ensure it matches the standard Ethereum address format. This validates that a string value contains the substring value. This validates that a string value contains any Unicode code points in the substring value. This validates that a string value contains the supplied rune value. This validates that a string value does not contain the substring value. This validates that a string value does not contain any Unicode code points in the substring value. This validates that a string value does not contain the supplied rune value. This validates that a string value starts with the supplied string value This validates that a string value ends with the supplied string value This validates that a string value does not start with the supplied string value This validates that a string value does not end with the supplied string value This validates that a string value contains a valid isbn10 or isbn13 value. This validates that a string value contains a valid isbn10 value. This validates that a string value contains a valid isbn13 value. This validates that a string value contains a valid UUID. Uppercase UUID values will not pass - use `uuid_rfc4122` instead. This validates that a string value contains a valid version 3 UUID. Uppercase UUID values will not pass - use `uuid3_rfc4122` instead. This validates that a string value contains a valid version 4 UUID. Uppercase UUID values will not pass - use `uuid4_rfc4122` instead. This validates that a string value contains a valid version 5 UUID. Uppercase UUID values will not pass - use `uuid5_rfc4122` instead. This validates that a string value contains a valid ULID value. This validates that a string value contains only ASCII characters. NOTE: if the string is blank, this validates as true. This validates that a string value contains only printable ASCII characters. NOTE: if the string is blank, this validates as true. This validates that a string value contains one or more multibyte characters. NOTE: if the string is blank, this validates as true. This validates that a string value contains a valid DataURI. NOTE: this will also validate that the data portion is valid base64 This validates that a string value contains a valid latitude. This validates that a string value contains a valid longitude. This validates that a string value contains a valid U.S. Social Security Number. This validates that a string value contains a valid IP Address. This validates that a string value contains a valid v4 IP Address. This validates that a string value contains a valid v6 IP Address. This validates that a string value contains a valid CIDR Address. This validates that a string value contains a valid v4 CIDR Address. This validates that a string value contains a valid v6 CIDR Address. This validates that a string value contains a valid resolvable TCP Address. This validates that a string value contains a valid resolvable v4 TCP Address. This validates that a string value contains a valid resolvable v6 TCP Address. This validates that a string value contains a valid resolvable UDP Address. This validates that a string value contains a valid resolvable v4 UDP Address. This validates that a string value contains a valid resolvable v6 UDP Address. This validates that a string value contains a valid resolvable IP Address. This validates that a string value contains a valid resolvable v4 IP Address. This validates that a string value contains a valid resolvable v6 IP Address. This validates that a string value contains a valid Unix Address. This validates that a string value contains a valid MAC Address. Note: See Go's ParseMAC for accepted formats and types: This validates that a string value is a valid Hostname according to RFC 952 https://tools.ietf.org/html/rfc952 This validates that a string value is a valid Hostname according to RFC 1123 https://tools.ietf.org/html/rfc1123 Full Qualified Domain Name (FQDN) This validates that a string value contains a valid FQDN. This validates that a string value appears to be an HTML element tag including those described at https://developer.mozilla.org/en-US/docs/Web/HTML/Element This validates that a string value is a proper character reference in decimal or hexadecimal format This validates that a string value is percent-encoded (URL encoded) according to https://tools.ietf.org/html/rfc3986#section-2.1 This validates that a string value contains a valid directory and that it exists on the machine. This is done using os.Stat, which is a platform independent function. This validates that a string value contains a valid directory but does not validate the existence of that directory. This is done using os.Stat, which is a platform independent function. It is safest to suffix the string with os.PathSeparator if the directory may not exist at the time of validation. This validates that a string value contains a valid DNS hostname and port that can be used to validate fields typically passed to sockets and connections. This validates that a string value is a valid datetime based on the supplied datetime format. Supplied format must match the official Go time format layout as documented in https://golang.org/pkg/time/ This validates that a string value is a valid country code based on iso3166-1 alpha-2 standard. see: https://www.iso.org/iso-3166-country-codes.html This validates that a string value is a valid country code based on iso3166-1 alpha-3 standard. see: https://www.iso.org/iso-3166-country-codes.html This validates that a string value is a valid country code based on iso3166-1 alpha-numeric standard. see: https://www.iso.org/iso-3166-country-codes.html This validates that a string value is a valid BCP 47 language tag, as parsed by language.Parse. More information on https://pkg.go.dev/golang.org/x/text/language BIC (SWIFT code) This validates that a string value is a valid Business Identifier Code (SWIFT code), defined in ISO 9362. More information on https://www.iso.org/standard/60390.html This validates that a string value is a valid dns RFC 1035 label, defined in RFC 1035. More information on https://datatracker.ietf.org/doc/html/rfc1035 This validates that a string value is a valid time zone based on the time zone database present on the system. Although empty value and Local value are allowed by time.LoadLocation golang function, they are not allowed by this validator. More information on https://golang.org/pkg/time/#LoadLocation This validates that a string value is a valid semver version, defined in Semantic Versioning 2.0.0. More information on https://semver.org/ This validates that a string value is a valid cve id, defined in cve mitre. More information on https://cve.mitre.org/ This validates that a string value contains a valid credit card number using Luhn algorithm. This validates that a string or (u)int value contains a valid checksum using the Luhn algorithm. This validates that a string is a valid 24 character hexadecimal string or valid connection string. Example: This validates that a string value contains a valid cron expression. This validates that a string is valid for use with SpiceDb for the indicated purpose. If no purpose is given, a purpose of 'id' is assumed. Alias Validators and Tags NOTE: When returning an error, the tag returned in "FieldError" will be the alias tag unless the dive tag is part of the alias. Everything after the dive tag is not reported as the alias tag. Also, the "ActualTag" in the before case will be the actual tag within the alias that failed. Here is a list of the current built in alias tags: Validator notes: A collection of validation rules that are frequently needed but are more complex than the ones found in the baked in validators. A non standard validator must be registered manually like you would with your own custom validation functions. Example of registration and use: Here is a list of the current non standard validators: This package panics when bad input is provided, this is by design, bad code like that should not make it to production.

Package validator implements value validations for structs and individual fields based on tags. It can also handle Cross-Field and Cross-Struct validation for nested structs and has the ability to dive into arrays and maps of any type. see more examples https://github.com/go-playground/validator/tree/v9/_examples Doing things this way is actually the way the standard library does, see the file.Open method here: The authors return type "error" to avoid the issue discussed in the following, where err is always != nil: Validator only InvalidValidationError for bad validation input, nil or ValidationErrors as type error; so, in your code all you need to do is check if the error returned is not nil, and if it's not check if error is InvalidValidationError ( if necessary, most of the time it isn't ) type cast it to type ValidationErrors like so err.(validator.ValidationErrors). Custom Validation functions can be added. Example: Cross-Field Validation can be done via the following tags: If, however, some custom cross-field validation is required, it can be done using a custom validation. Why not just have cross-fields validation tags (i.e. only eqcsfield and not eqfield)? The reason is efficiency. If you want to check a field within the same struct "eqfield" only has to find the field on the same struct (1 level). But, if we used "eqcsfield" it could be multiple levels down. Example: Multiple validators on a field will process in the order defined. Example: Bad Validator definitions are not handled by the library. Example: Baked In Cross-Field validation only compares fields on the same struct. If Cross-Field + Cross-Struct validation is needed you should implement your own custom validator. Comma (",") is the default separator of validation tags. If you wish to have a comma included within the parameter (i.e. excludesall=,) you will need to use the UTF-8 hex representation 0x2C, which is replaced in the code as a comma, so the above will become excludesall=0x2C. Pipe ("|") is the 'or' validation tags deparator. If you wish to have a pipe included within the parameter i.e. excludesall=| you will need to use the UTF-8 hex representation 0x7C, which is replaced in the code as a pipe, so the above will become excludesall=0x7C Here is a list of the current built in validators: Tells the validation to skip this struct field; this is particularly handy in ignoring embedded structs from being validated. (Usage: -) This is the 'or' operator allowing multiple validators to be used and accepted. (Usage: rbg|rgba) <-- this would allow either rgb or rgba colors to be accepted. This can also be combined with 'and' for example ( Usage: omitempty,rgb|rgba) When a field that is a nested struct is encountered, and contains this flag any validation on the nested struct will be run, but none of the nested struct fields will be validated. This is useful if inside of your program you know the struct will be valid, but need to verify it has been assigned. NOTE: only "required" and "omitempty" can be used on a struct itself. Same as structonly tag except that any struct level validations will not run. Allows conditional validation, for example if a field is not set with a value (Determined by the "required" validator) then other validation such as min or max won't run, but if a value is set validation will run. This tells the validator to dive into a slice, array or map and validate that level of the slice, array or map with the validation tags that follow. Multidimensional nesting is also supported, each level you wish to dive will require another dive tag. dive has some sub-tags, 'keys' & 'endkeys', please see the Keys & EndKeys section just below. Example #1 Example #2 Keys & EndKeys These are to be used together directly after the dive tag and tells the validator that anything between 'keys' and 'endkeys' applies to the keys of a map and not the values; think of it like the 'dive' tag, but for map keys instead of values. Multidimensional nesting is also supported, each level you wish to validate will require another 'keys' and 'endkeys' tag. These tags are only valid for maps. Example #1 Example #2 This validates that the value is not the data types default zero value. For numbers ensures value is not zero. For strings ensures value is not "". For slices, maps, pointers, interfaces, channels and functions ensures the value is not nil. The field under validation must be present and not empty only if any of the other specified fields are present. For strings ensures value is not "". For slices, maps, pointers, interfaces, channels and functions ensures the value is not nil. Examples: The field under validation must be present and not empty only if all of the other specified fields are present. For strings ensures value is not "". For slices, maps, pointers, interfaces, channels and functions ensures the value is not nil. Example: The field under validation must be present and not empty only when any of the other specified fields are not present. For strings ensures value is not "". For slices, maps, pointers, interfaces, channels and functions ensures the value is not nil. Examples: The field under validation must be present and not empty only when all of the other specified fields are not present. For strings ensures value is not "". For slices, maps, pointers, interfaces, channels and functions ensures the value is not nil. Example: This validates that the value is the default value and is almost the opposite of required. For numbers, length will ensure that the value is equal to the parameter given. For strings, it checks that the string length is exactly that number of characters. For slices, arrays, and maps, validates the number of items. For numbers, max will ensure that the value is less than or equal to the parameter given. For strings, it checks that the string length is at most that number of characters. For slices, arrays, and maps, validates the number of items. For numbers, min will ensure that the value is greater or equal to the parameter given. For strings, it checks that the string length is at least that number of characters. For slices, arrays, and maps, validates the number of items. For strings & numbers, eq will ensure that the value is equal to the parameter given. For slices, arrays, and maps, validates the number of items. For strings & numbers, ne will ensure that the value is not equal to the parameter given. For slices, arrays, and maps, validates the number of items. For strings, ints, and uints, oneof will ensure that the value is one of the values in the parameter. The parameter should be a list of values separated by whitespace. Values may be strings or numbers. For numbers, this will ensure that the value is greater than the parameter given. For strings, it checks that the string length is greater than that number of characters. For slices, arrays and maps it validates the number of items. Example #1 Example #2 (time.Time) For time.Time ensures the time value is greater than time.Now.UTC(). Same as 'min' above. Kept both to make terminology with 'len' easier. Example #1 Example #2 (time.Time) For time.Time ensures the time value is greater than or equal to time.Now.UTC(). For numbers, this will ensure that the value is less than the parameter given. For strings, it checks that the string length is less than that number of characters. For slices, arrays, and maps it validates the number of items. Example #1 Example #2 (time.Time) For time.Time ensures the time value is less than time.Now.UTC(). Same as 'max' above. Kept both to make terminology with 'len' easier. Example #1 Example #2 (time.Time) For time.Time ensures the time value is less than or equal to time.Now.UTC(). This will validate the field value against another fields value either within a struct or passed in field. Example #1: Example #2: Field Equals Another Field (relative) This does the same as eqfield except that it validates the field provided relative to the top level struct. This will validate the field value against another fields value either within a struct or passed in field. Examples: Field Does Not Equal Another Field (relative) This does the same as nefield except that it validates the field provided relative to the top level struct. Only valid for Numbers and time.Time types, this will validate the field value against another fields value either within a struct or passed in field. usage examples are for validation of a Start and End date: Example #1: Example #2: This does the same as gtfield except that it validates the field provided relative to the top level struct. Only valid for Numbers and time.Time types, this will validate the field value against another fields value either within a struct or passed in field. usage examples are for validation of a Start and End date: Example #1: Example #2: This does the same as gtefield except that it validates the field provided relative to the top level struct. Only valid for Numbers and time.Time types, this will validate the field value against another fields value either within a struct or passed in field. usage examples are for validation of a Start and End date: Example #1: Example #2: This does the same as ltfield except that it validates the field provided relative to the top level struct. Only valid for Numbers and time.Time types, this will validate the field value against another fields value either within a struct or passed in field. usage examples are for validation of a Start and End date: Example #1: Example #2: This does the same as ltefield except that it validates the field provided relative to the top level struct. This does the same as contains except for struct fields. It should only be used with string types. See the behavior of reflect.Value.String() for behavior on other types. This does the same as excludes except for struct fields. It should only be used with string types. See the behavior of reflect.Value.String() for behavior on other types. For arrays & slices, unique will ensure that there are no duplicates. For maps, unique will ensure that there are no duplicate values. For slices of struct, unique will ensure that there are no duplicate values in a field of the struct specified via a parameter. This validates that a string value contains ASCII alpha characters only This validates that a string value contains ASCII alphanumeric characters only This validates that a string value contains unicode alpha characters only This validates that a string value contains unicode alphanumeric characters only This validates that a string value contains a basic numeric value. basic excludes exponents etc... for integers or float it returns true. This validates that a string value contains a valid hexadecimal. This validates that a string value contains a valid hex color including hashtag (#) This validates that a string value contains a valid rgb color This validates that a string value contains a valid rgba color This validates that a string value contains a valid hsl color This validates that a string value contains a valid hsla color This validates that a string value contains a valid email This may not conform to all possibilities of any rfc standard, but neither does any email provider accept all possibilities. This validates that a string value contains a valid file path and that the file exists on the machine. This is done using os.Stat, which is a platform independent function. This validates that a string value contains a valid url This will accept any url the golang request uri accepts but must contain a schema for example http:// or rtmp:// This validates that a string value contains a valid uri This will accept any uri the golang request uri accepts This validataes that a string value contains a valid URN according to the RFC 2141 spec. This validates that a string value contains a valid base64 value. Although an empty string is valid base64 this will report an empty string as an error, if you wish to accept an empty string as valid you can use this with the omitempty tag. This validates that a string value contains a valid base64 URL safe value according the the RFC4648 spec. Although an empty string is a valid base64 URL safe value, this will report an empty string as an error, if you wish to accept an empty string as valid you can use this with the omitempty tag. This validates that a string value contains a valid bitcoin address. The format of the string is checked to ensure it matches one of the three formats P2PKH, P2SH and performs checksum validation. Bitcoin Bech32 Address (segwit) This validates that a string value contains a valid bitcoin Bech32 address as defined by bip-0173 (https://github.com/bitcoin/bips/blob/master/bip-0173.mediawiki) Special thanks to Pieter Wuille for providng reference implementations. This validates that a string value contains a valid ethereum address. The format of the string is checked to ensure it matches the standard Ethereum address format Full validation is blocked by https://github.com/golang/crypto/pull/28 This validates that a string value contains the substring value. This validates that a string value contains any Unicode code points in the substring value. This validates that a string value contains the supplied rune value. This validates that a string value does not contain the substring value. This validates that a string value does not contain any Unicode code points in the substring value. This validates that a string value does not contain the supplied rune value. This validates that a string value starts with the supplied string value This validates that a string value ends with the supplied string value This validates that a string value contains a valid isbn10 or isbn13 value. This validates that a string value contains a valid isbn10 value. This validates that a string value contains a valid isbn13 value. This validates that a string value contains a valid UUID. Uppercase UUID values will not pass - use `uuid_rfc4122` instead. This validates that a string value contains a valid version 3 UUID. Uppercase UUID values will not pass - use `uuid3_rfc4122` instead. This validates that a string value contains a valid version 4 UUID. Uppercase UUID values will not pass - use `uuid4_rfc4122` instead. This validates that a string value contains a valid version 5 UUID. Uppercase UUID values will not pass - use `uuid5_rfc4122` instead. This validates that a string value contains only ASCII characters. NOTE: if the string is blank, this validates as true. This validates that a string value contains only printable ASCII characters. NOTE: if the string is blank, this validates as true. This validates that a string value contains one or more multibyte characters. NOTE: if the string is blank, this validates as true. This validates that a string value contains a valid DataURI. NOTE: this will also validate that the data portion is valid base64 This validates that a string value contains a valid latitude. This validates that a string value contains a valid longitude. This validates that a string value contains a valid U.S. Social Security Number. This validates that a string value contains a valid IP Address. This validates that a string value contains a valid v4 IP Address. This validates that a string value contains a valid v6 IP Address. This validates that a string value contains a valid CIDR Address. This validates that a string value contains a valid v4 CIDR Address. This validates that a string value contains a valid v6 CIDR Address. This validates that a string value contains a valid resolvable TCP Address. This validates that a string value contains a valid resolvable v4 TCP Address. This validates that a string value contains a valid resolvable v6 TCP Address. This validates that a string value contains a valid resolvable UDP Address. This validates that a string value contains a valid resolvable v4 UDP Address. This validates that a string value contains a valid resolvable v6 UDP Address. This validates that a string value contains a valid resolvable IP Address. This validates that a string value contains a valid resolvable v4 IP Address. This validates that a string value contains a valid resolvable v6 IP Address. This validates that a string value contains a valid Unix Address. This validates that a string value contains a valid MAC Address. Note: See Go's ParseMAC for accepted formats and types: This validates that a string value is a valid Hostname according to RFC 952 https://tools.ietf.org/html/rfc952 This validates that a string value is a valid Hostname according to RFC 1123 https://tools.ietf.org/html/rfc1123 Full Qualified Domain Name (FQDN) This validates that a string value contains a valid FQDN. This validates that a string value appears to be an HTML element tag including those described at https://developer.mozilla.org/en-US/docs/Web/HTML/Element This validates that a string value is a proper character reference in decimal or hexadecimal format This validates that a string value is percent-encoded (URL encoded) according to https://tools.ietf.org/html/rfc3986#section-2.1 This validates that a string value contains a valid directory and that it exists on the machine. This is done using os.Stat, which is a platform independent function. NOTE: When returning an error, the tag returned in "FieldError" will be the alias tag unless the dive tag is part of the alias. Everything after the dive tag is not reported as the alias tag. Also, the "ActualTag" in the before case will be the actual tag within the alias that failed. Here is a list of the current built in alias tags: Validator notes: A collection of validation rules that are frequently needed but are more complex than the ones found in the baked in validators. A non standard validator must be registered manually like you would with your own custom validation functions. Example of registration and use: Here is a list of the current non standard validators: This package panics when bad input is provided, this is by design, bad code like that should not make it to production.

Package validator implements value validations for structs and individual fields based on tags. It can also handle Cross-Field and Cross-Struct validation for nested structs and has the ability to dive into arrays and maps of any type. see more examples https://github.com/go-playground/validator/tree/v9/_examples Doing things this way is actually the way the standard library does, see the file.Open method here: The authors return type "error" to avoid the issue discussed in the following, where err is always != nil: Validator only InvalidValidationError for bad validation input, nil or ValidationErrors as type error; so, in your code all you need to do is check if the error returned is not nil, and if it's not check if error is InvalidValidationError ( if necessary, most of the time it isn't ) type cast it to type ValidationErrors like so err.(validator.ValidationErrors). Custom Validation functions can be added. Example: Cross-Field Validation can be done via the following tags: If, however, some custom cross-field validation is required, it can be done using a custom validation. Why not just have cross-fields validation tags (i.e. only eqcsfield and not eqfield)? The reason is efficiency. If you want to check a field within the same struct "eqfield" only has to find the field on the same struct (1 level). But, if we used "eqcsfield" it could be multiple levels down. Example: Multiple validators on a field will process in the order defined. Example: Bad Validator definitions are not handled by the library. Example: Baked In Cross-Field validation only compares fields on the same struct. If Cross-Field + Cross-Struct validation is needed you should implement your own custom validator. Comma (",") is the default separator of validation tags. If you wish to have a comma included within the parameter (i.e. excludesall=,) you will need to use the UTF-8 hex representation 0x2C, which is replaced in the code as a comma, so the above will become excludesall=0x2C. Pipe ("|") is the 'or' validation tags deparator. If you wish to have a pipe included within the parameter i.e. excludesall=| you will need to use the UTF-8 hex representation 0x7C, which is replaced in the code as a pipe, so the above will become excludesall=0x7C Here is a list of the current built in validators: Tells the validation to skip this struct field; this is particularly handy in ignoring embedded structs from being validated. (Usage: -) This is the 'or' operator allowing multiple validators to be used and accepted. (Usage: rbg|rgba) <-- this would allow either rgb or rgba colors to be accepted. This can also be combined with 'and' for example ( Usage: omitempty,rgb|rgba) When a field that is a nested struct is encountered, and contains this flag any validation on the nested struct will be run, but none of the nested struct fields will be validated. This is useful if inside of your program you know the struct will be valid, but need to verify it has been assigned. NOTE: only "required" and "omitempty" can be used on a struct itself. Same as structonly tag except that any struct level validations will not run. Allows conditional validation, for example if a field is not set with a value (Determined by the "required" validator) then other validation such as min or max won't run, but if a value is set validation will run. This tells the validator to dive into a slice, array or map and validate that level of the slice, array or map with the validation tags that follow. Multidimensional nesting is also supported, each level you wish to dive will require another dive tag. dive has some sub-tags, 'keys' & 'endkeys', please see the Keys & EndKeys section just below. Example #1 Example #2 Keys & EndKeys These are to be used together directly after the dive tag and tells the validator that anything between 'keys' and 'endkeys' applies to the keys of a map and not the values; think of it like the 'dive' tag, but for map keys instead of values. Multidimensional nesting is also supported, each level you wish to validate will require another 'keys' and 'endkeys' tag. These tags are only valid for maps. Example #1 Example #2 This validates that the value is not the data types default zero value. For numbers ensures value is not zero. For strings ensures value is not "". For slices, maps, pointers, interfaces, channels and functions ensures the value is not nil. The field under validation must be present and not empty only if any of the other specified fields are present. For strings ensures value is not "". For slices, maps, pointers, interfaces, channels and functions ensures the value is not nil. Examples: The field under validation must be present and not empty only if all of the other specified fields are present. For strings ensures value is not "". For slices, maps, pointers, interfaces, channels and functions ensures the value is not nil. Example: The field under validation must be present and not empty only when any of the other specified fields are not present. For strings ensures value is not "". For slices, maps, pointers, interfaces, channels and functions ensures the value is not nil. Examples: The field under validation must be present and not empty only when all of the other specified fields are not present. For strings ensures value is not "". For slices, maps, pointers, interfaces, channels and functions ensures the value is not nil. Example: This validates that the value is the default value and is almost the opposite of required. For numbers, length will ensure that the value is equal to the parameter given. For strings, it checks that the string length is exactly that number of characters. For slices, arrays, and maps, validates the number of items. For numbers, max will ensure that the value is less than or equal to the parameter given. For strings, it checks that the string length is at most that number of characters. For slices, arrays, and maps, validates the number of items. For numbers, min will ensure that the value is greater or equal to the parameter given. For strings, it checks that the string length is at least that number of characters. For slices, arrays, and maps, validates the number of items. For strings & numbers, eq will ensure that the value is equal to the parameter given. For slices, arrays, and maps, validates the number of items. For strings & numbers, ne will ensure that the value is not equal to the parameter given. For slices, arrays, and maps, validates the number of items. For strings, ints, and uints, oneof will ensure that the value is one of the values in the parameter. The parameter should be a list of values separated by whitespace. Values may be strings or numbers. For numbers, this will ensure that the value is greater than the parameter given. For strings, it checks that the string length is greater than that number of characters. For slices, arrays and maps it validates the number of items. Example #1 Example #2 (time.Time) For time.Time ensures the time value is greater than time.Now.UTC(). Same as 'min' above. Kept both to make terminology with 'len' easier. Example #1 Example #2 (time.Time) For time.Time ensures the time value is greater than or equal to time.Now.UTC(). For numbers, this will ensure that the value is less than the parameter given. For strings, it checks that the string length is less than that number of characters. For slices, arrays, and maps it validates the number of items. Example #1 Example #2 (time.Time) For time.Time ensures the time value is less than time.Now.UTC(). Same as 'max' above. Kept both to make terminology with 'len' easier. Example #1 Example #2 (time.Time) For time.Time ensures the time value is less than or equal to time.Now.UTC(). This will validate the field value against another fields value either within a struct or passed in field. Example #1: Example #2: Field Equals Another Field (relative) This does the same as eqfield except that it validates the field provided relative to the top level struct. This will validate the field value against another fields value either within a struct or passed in field. Examples: Field Does Not Equal Another Field (relative) This does the same as nefield except that it validates the field provided relative to the top level struct. Only valid for Numbers and time.Time types, this will validate the field value against another fields value either within a struct or passed in field. usage examples are for validation of a Start and End date: Example #1: Example #2: This does the same as gtfield except that it validates the field provided relative to the top level struct. Only valid for Numbers and time.Time types, this will validate the field value against another fields value either within a struct or passed in field. usage examples are for validation of a Start and End date: Example #1: Example #2: This does the same as gtefield except that it validates the field provided relative to the top level struct. Only valid for Numbers and time.Time types, this will validate the field value against another fields value either within a struct or passed in field. usage examples are for validation of a Start and End date: Example #1: Example #2: This does the same as ltfield except that it validates the field provided relative to the top level struct. Only valid for Numbers and time.Time types, this will validate the field value against another fields value either within a struct or passed in field. usage examples are for validation of a Start and End date: Example #1: Example #2: This does the same as ltefield except that it validates the field provided relative to the top level struct. This does the same as contains except for struct fields. It should only be used with string types. See the behavior of reflect.Value.String() for behavior on other types. This does the same as excludes except for struct fields. It should only be used with string types. See the behavior of reflect.Value.String() for behavior on other types. For arrays & slices, unique will ensure that there are no duplicates. For maps, unique will ensure that there are no duplicate values. For slices of struct, unique will ensure that there are no duplicate values in a field of the struct specified via a parameter. This validates that a string value contains ASCII alpha characters only This validates that a string value contains ASCII alphanumeric characters only This validates that a string value contains unicode alpha characters only This validates that a string value contains unicode alphanumeric characters only This validates that a string value contains a basic numeric value. basic excludes exponents etc... for integers or float it returns true. This validates that a string value contains a valid hexadecimal. This validates that a string value contains a valid hex color including hashtag (#) This validates that a string value contains a valid rgb color This validates that a string value contains a valid rgba color This validates that a string value contains a valid hsl color This validates that a string value contains a valid hsla color This validates that a string value contains a valid email This may not conform to all possibilities of any rfc standard, but neither does any email provider accept all possibilities. This validates that a string value contains a valid file path and that the file exists on the machine. This is done using os.Stat, which is a platform independent function. This validates that a string value contains a valid url This will accept any url the golang request uri accepts but must contain a schema for example http:// or rtmp:// This validates that a string value contains a valid uri This will accept any uri the golang request uri accepts This validataes that a string value contains a valid URN according to the RFC 2141 spec. This validates that a string value contains a valid base64 value. Although an empty string is valid base64 this will report an empty string as an error, if you wish to accept an empty string as valid you can use this with the omitempty tag. This validates that a string value contains a valid base64 URL safe value according the the RFC4648 spec. Although an empty string is a valid base64 URL safe value, this will report an empty string as an error, if you wish to accept an empty string as valid you can use this with the omitempty tag. This validates that a string value contains a valid bitcoin address. The format of the string is checked to ensure it matches one of the three formats P2PKH, P2SH and performs checksum validation. Bitcoin Bech32 Address (segwit) This validates that a string value contains a valid bitcoin Bech32 address as defined by bip-0173 (https://github.com/bitcoin/bips/blob/master/bip-0173.mediawiki) Special thanks to Pieter Wuille for providng reference implementations. This validates that a string value contains a valid ethereum address. The format of the string is checked to ensure it matches the standard Ethereum address format Full validation is blocked by https://github.com/golang/crypto/pull/28 This validates that a string value contains the substring value. This validates that a string value contains any Unicode code points in the substring value. This validates that a string value contains the supplied rune value. This validates that a string value does not contain the substring value. This validates that a string value does not contain any Unicode code points in the substring value. This validates that a string value does not contain the supplied rune value. This validates that a string value starts with the supplied string value This validates that a string value ends with the supplied string value This validates that a string value contains a valid isbn10 or isbn13 value. This validates that a string value contains a valid isbn10 value. This validates that a string value contains a valid isbn13 value. This validates that a string value contains a valid UUID. Uppercase UUID values will not pass - use `uuid_rfc4122` instead. This validates that a string value contains a valid version 3 UUID. Uppercase UUID values will not pass - use `uuid3_rfc4122` instead. This validates that a string value contains a valid version 4 UUID. Uppercase UUID values will not pass - use `uuid4_rfc4122` instead. This validates that a string value contains a valid version 5 UUID. Uppercase UUID values will not pass - use `uuid5_rfc4122` instead. This validates that a string value contains only ASCII characters. NOTE: if the string is blank, this validates as true. This validates that a string value contains only printable ASCII characters. NOTE: if the string is blank, this validates as true. This validates that a string value contains one or more multibyte characters. NOTE: if the string is blank, this validates as true. This validates that a string value contains a valid DataURI. NOTE: this will also validate that the data portion is valid base64 This validates that a string value contains a valid latitude. This validates that a string value contains a valid longitude. This validates that a string value contains a valid U.S. Social Security Number. This validates that a string value contains a valid IP Address. This validates that a string value contains a valid v4 IP Address. This validates that a string value contains a valid v6 IP Address. This validates that a string value contains a valid CIDR Address. This validates that a string value contains a valid v4 CIDR Address. This validates that a string value contains a valid v6 CIDR Address. This validates that a string value contains a valid resolvable TCP Address. This validates that a string value contains a valid resolvable v4 TCP Address. This validates that a string value contains a valid resolvable v6 TCP Address. This validates that a string value contains a valid resolvable UDP Address. This validates that a string value contains a valid resolvable v4 UDP Address. This validates that a string value contains a valid resolvable v6 UDP Address. This validates that a string value contains a valid resolvable IP Address. This validates that a string value contains a valid resolvable v4 IP Address. This validates that a string value contains a valid resolvable v6 IP Address. This validates that a string value contains a valid Unix Address. This validates that a string value contains a valid MAC Address. Note: See Go's ParseMAC for accepted formats and types: This validates that a string value is a valid Hostname according to RFC 952 https://tools.ietf.org/html/rfc952 This validates that a string value is a valid Hostname according to RFC 1123 https://tools.ietf.org/html/rfc1123 Full Qualified Domain Name (FQDN) This validates that a string value contains a valid FQDN. This validates that a string value appears to be an HTML element tag including those described at https://developer.mozilla.org/en-US/docs/Web/HTML/Element This validates that a string value is a proper character reference in decimal or hexadecimal format This validates that a string value is percent-encoded (URL encoded) according to https://tools.ietf.org/html/rfc3986#section-2.1 This validates that a string value contains a valid directory and that it exists on the machine. This is done using os.Stat, which is a platform independent function. NOTE: When returning an error, the tag returned in "FieldError" will be the alias tag unless the dive tag is part of the alias. Everything after the dive tag is not reported as the alias tag. Also, the "ActualTag" in the before case will be the actual tag within the alias that failed. Here is a list of the current built in alias tags: Validator notes: A collection of validation rules that are frequently needed but are more complex than the ones found in the baked in validators. A non standard validator must be registered manually like you would with your own custom validation functions. Example of registration and use: Here is a list of the current non standard validators: This package panics when bad input is provided, this is by design, bad code like that should not make it to production.

Package tea provides an Elm inspired functional framework for interactive command-line programs.

Package dns implements a full featured interface to the Domain Name System. Both server- and client-side programming is supported. The package allows complete control over what is sent out to the DNS. The API follows the less-is-more principle, by presenting a small, clean interface. It supports (asynchronous) querying/replying, incoming/outgoing zone transfers, TSIG, EDNS0, dynamic updates, notifies and DNSSEC validation/signing. Note that domain names MUST be fully qualified before sending them, unqualified names in a message will result in a packing failure. Resource records are native types. They are not stored in wire format. Basic usage pattern for creating a new resource record: Or directly from a string: Or when the default origin (.) and TTL (3600) and class (IN) suit you: Or even: In the DNS messages are exchanged, these messages contain resource records (sets). Use pattern for creating a message: Or when not certain if the domain name is fully qualified: The message m is now a message with the question section set to ask the MX records for the miek.nl. zone. The following is slightly more verbose, but more flexible: After creating a message it can be sent. Basic use pattern for synchronous querying the DNS at a server configured on 127.0.0.1 and port 53: Suppressing multiple outstanding queries (with the same question, type and class) is as easy as setting: More advanced options are available using a net.Dialer and the corresponding API. For example it is possible to set a timeout, or to specify a source IP address and port to use for the connection: If these "advanced" features are not needed, a simple UDP query can be sent, with: When this functions returns you will get dns message. A dns message consists out of four sections. The question section: in.Question, the answer section: in.Answer, the authority section: in.Ns and the additional section: in.Extra. Each of these sections (except the Question section) contain a []RR. Basic use pattern for accessing the rdata of a TXT RR as the first RR in the Answer section: Both domain names and TXT character strings are converted to presentation form both when unpacked and when converted to strings. For TXT character strings, tabs, carriage returns and line feeds will be converted to \t, \r and \n respectively. Back slashes and quotations marks will be escaped. Bytes below 32 and above 127 will be converted to \DDD form. For domain names, in addition to the above rules brackets, periods, spaces, semicolons and the at symbol are escaped. DNSSEC (DNS Security Extension) adds a layer of security to the DNS. It uses public key cryptography to sign resource records. The public keys are stored in DNSKEY records and the signatures in RRSIG records. Requesting DNSSEC information for a zone is done by adding the DO (DNSSEC OK) bit to a request. Signature generation, signature verification and key generation are all supported. Dynamic updates reuses the DNS message format, but renames three of the sections. Question is Zone, Answer is Prerequisite, Authority is Update, only the Additional is not renamed. See RFC 2136 for the gory details. You can set a rather complex set of rules for the existence of absence of certain resource records or names in a zone to specify if resource records should be added or removed. The table from RFC 2136 supplemented with the Go DNS function shows which functions exist to specify the prerequisites. The prerequisite section can also be left empty. If you have decided on the prerequisites you can tell what RRs should be added or deleted. The next table shows the options you have and what functions to call. An TSIG or transaction signature adds a HMAC TSIG record to each message sent. The supported algorithms include: HmacMD5, HmacSHA1, HmacSHA256 and HmacSHA512. Basic use pattern when querying with a TSIG name "axfr." (note that these key names must be fully qualified - as they are domain names) and the base64 secret "so6ZGir4GPAqINNh9U5c3A==": If an incoming message contains a TSIG record it MUST be the last record in the additional section (RFC2845 3.2). This means that you should make the call to SetTsig last, right before executing the query. If you make any changes to the RRset after calling SetTsig() the signature will be incorrect. When requesting an zone transfer (almost all TSIG usage is when requesting zone transfers), with TSIG, this is the basic use pattern. In this example we request an AXFR for miek.nl. with TSIG key named "axfr." and secret "so6ZGir4GPAqINNh9U5c3A==" and using the server 176.58.119.54: You can now read the records from the transfer as they come in. Each envelope is checked with TSIG. If something is not correct an error is returned. Basic use pattern validating and replying to a message that has TSIG set. RFC 6895 sets aside a range of type codes for private use. This range is 65,280 - 65,534 (0xFF00 - 0xFFFE). When experimenting with new Resource Records these can be used, before requesting an official type code from IANA. See https://miek.nl/2014/September/21/idn-and-private-rr-in-go-dns/ for more information. EDNS0 is an extension mechanism for the DNS defined in RFC 2671 and updated by RFC 6891. It defines an new RR type, the OPT RR, which is then completely abused. Basic use pattern for creating an (empty) OPT RR: The rdata of an OPT RR consists out of a slice of EDNS0 (RFC 6891) interfaces. Currently only a few have been standardized: EDNS0_NSID (RFC 5001) and EDNS0_SUBNET (draft-vandergaast-edns-client-subnet-02). Note that these options may be combined in an OPT RR. Basic use pattern for a server to check if (and which) options are set: SIG(0) From RFC 2931: It works like TSIG, except that SIG(0) uses public key cryptography, instead of the shared secret approach in TSIG. Supported algorithms: DSA, ECDSAP256SHA256, ECDSAP384SHA384, RSASHA1, RSASHA256 and RSASHA512. Signing subsequent messages in multi-message sessions is not implemented.

Package dns implements a full featured interface to the Domain Name System. Both server- and client-side programming is supported. The package allows complete control over what is sent out to the DNS. The API follows the less-is-more principle, by presenting a small, clean interface. It supports (asynchronous) querying/replying, incoming/outgoing zone transfers, TSIG, EDNS0, dynamic updates, notifies and DNSSEC validation/signing. Note that domain names MUST be fully qualified before sending them, unqualified names in a message will result in a packing failure. Resource records are native types. They are not stored in wire format. Basic usage pattern for creating a new resource record: Or directly from a string: Or when the default origin (.) and TTL (3600) and class (IN) suit you: Or even: In the DNS messages are exchanged, these messages contain resource records (sets). Use pattern for creating a message: Or when not certain if the domain name is fully qualified: The message m is now a message with the question section set to ask the MX records for the miek.nl. zone. The following is slightly more verbose, but more flexible: After creating a message it can be sent. Basic use pattern for synchronous querying the DNS at a server configured on 127.0.0.1 and port 53: Suppressing multiple outstanding queries (with the same question, type and class) is as easy as setting: More advanced options are available using a net.Dialer and the corresponding API. For example it is possible to set a timeout, or to specify a source IP address and port to use for the connection: If these "advanced" features are not needed, a simple UDP query can be sent, with: When this functions returns you will get dns message. A dns message consists out of four sections. The question section: in.Question, the answer section: in.Answer, the authority section: in.Ns and the additional section: in.Extra. Each of these sections (except the Question section) contain a []RR. Basic use pattern for accessing the rdata of a TXT RR as the first RR in the Answer section: Both domain names and TXT character strings are converted to presentation form both when unpacked and when converted to strings. For TXT character strings, tabs, carriage returns and line feeds will be converted to \t, \r and \n respectively. Back slashes and quotations marks will be escaped. Bytes below 32 and above 127 will be converted to \DDD form. For domain names, in addition to the above rules brackets, periods, spaces, semicolons and the at symbol are escaped. DNSSEC (DNS Security Extension) adds a layer of security to the DNS. It uses public key cryptography to sign resource records. The public keys are stored in DNSKEY records and the signatures in RRSIG records. Requesting DNSSEC information for a zone is done by adding the DO (DNSSEC OK) bit to a request. Signature generation, signature verification and key generation are all supported. Dynamic updates reuses the DNS message format, but renames three of the sections. Question is Zone, Answer is Prerequisite, Authority is Update, only the Additional is not renamed. See RFC 2136 for the gory details. You can set a rather complex set of rules for the existence of absence of certain resource records or names in a zone to specify if resource records should be added or removed. The table from RFC 2136 supplemented with the Go DNS function shows which functions exist to specify the prerequisites. The prerequisite section can also be left empty. If you have decided on the prerequisites you can tell what RRs should be added or deleted. The next table shows the options you have and what functions to call. An TSIG or transaction signature adds a HMAC TSIG record to each message sent. The supported algorithms include: HmacMD5, HmacSHA1, HmacSHA256 and HmacSHA512. Basic use pattern when querying with a TSIG name "axfr." (note that these key names must be fully qualified - as they are domain names) and the base64 secret "so6ZGir4GPAqINNh9U5c3A==": If an incoming message contains a TSIG record it MUST be the last record in the additional section (RFC2845 3.2). This means that you should make the call to SetTsig last, right before executing the query. If you make any changes to the RRset after calling SetTsig() the signature will be incorrect. When requesting an zone transfer (almost all TSIG usage is when requesting zone transfers), with TSIG, this is the basic use pattern. In this example we request an AXFR for miek.nl. with TSIG key named "axfr." and secret "so6ZGir4GPAqINNh9U5c3A==" and using the server 176.58.119.54: You can now read the records from the transfer as they come in. Each envelope is checked with TSIG. If something is not correct an error is returned. Basic use pattern validating and replying to a message that has TSIG set. RFC 6895 sets aside a range of type codes for private use. This range is 65,280 - 65,534 (0xFF00 - 0xFFFE). When experimenting with new Resource Records these can be used, before requesting an official type code from IANA. See https://miek.nl/2014/September/21/idn-and-private-rr-in-go-dns/ for more information. EDNS0 is an extension mechanism for the DNS defined in RFC 2671 and updated by RFC 6891. It defines an new RR type, the OPT RR, which is then completely abused. Basic use pattern for creating an (empty) OPT RR: The rdata of an OPT RR consists out of a slice of EDNS0 (RFC 6891) interfaces. Currently only a few have been standardized: EDNS0_NSID (RFC 5001) and EDNS0_SUBNET (draft-vandergaast-edns-client-subnet-02). Note that these options may be combined in an OPT RR. Basic use pattern for a server to check if (and which) options are set: SIG(0) From RFC 2931: It works like TSIG, except that SIG(0) uses public key cryptography, instead of the shared secret approach in TSIG. Supported algorithms: DSA, ECDSAP256SHA256, ECDSAP384SHA384, RSASHA1, RSASHA256 and RSASHA512. Signing subsequent messages in multi-message sessions is not implemented.

Package bindata converts any file into manageable Go source code. Useful for embedding binary data into a go program. The file data is optionally gzip compressed before being converted to a raw byte slice. The following paragraphs cover some of the customization options which can be specified in the Config struct, which must be passed into the Translate() call. When used with the `Debug` option, the generated code does not actually include the asset data. Instead, it generates function stubs which load the data from the original file on disk. The asset API remains identical between debug and release builds, so your code will not have to change. This is useful during development when you expect the assets to change often. The host application using these assets uses the same API in both cases and will not have to care where the actual data comes from. An example is a Go webserver with some embedded, static web content like HTML, JS and CSS files. While developing it, you do not want to rebuild the whole server and restart it every time you make a change to a bit of javascript. You just want to build and launch the server once. Then just press refresh in the browser to see those changes. Embedding the assets with the `debug` flag allows you to do just that. When you are finished developing and ready for deployment, just re-invoke `go-bindata` without the `-debug` flag. It will now embed the latest version of the assets. The `MemCopy` option will alter the way the output file is generated. If false, it will employ a hack that allows us to read the file data directly from the compiled program's `.rodata` section. This ensures that when we call call our generated function, we omit unnecessary memcopies. The downside of this, is that it requires dependencies on the `reflect` and `unsafe` packages. These may be restricted on platforms like AppEngine and thus prevent you from using this mode. Another disadvantage is that the byte slice we create, is strictly read-only. For most use-cases this is not a problem, but if you ever try to alter the returned byte slice, a runtime panic is thrown. Use this mode only on target platforms where memory constraints are an issue. The default behaviour is to use the old code generation method. This prevents the two previously mentioned issues, but will employ at least one extra memcopy and thus increase memory requirements. For instance, consider the following two examples: This would be the default mode, using an extra memcopy but gives a safe implementation without dependencies on `reflect` and `unsafe`: Here is the same functionality, but uses the `.rodata` hack. The byte slice returned from this example can not be written to without generating a runtime error. The Compress option indicates that the supplied assets are GZIP compressed before being turned into Go code. The data should still be accessed through a function call, so nothing changes in the API. This feature is useful if you do not care for compression, or the supplied resource is already compressed. Doing it again would not add any value and may even increase the size of the data. The default behaviour of the program is to use compression. The keys used in the `_bindata` map are the same as the input file name passed to `go-bindata`. This includes the path. In most cases, this is not desirable, as it puts potentially sensitive information in your code base. For this purpose, the tool supplies another command line flag `-prefix`. This accepts a portion of a path name, which should be stripped off from the map keys and function names. For example, running without the `-prefix` flag, we get: Running with the `-prefix` flag, we get: With the optional Tags field, you can specify any go build tags that must be fulfilled for the output file to be included in a build. This is useful when including binary data in multiple formats, where the desired format is specified at build time with the appropriate tags. The tags are appended to a `// +build` line in the beginning of the output file and must follow the build tags syntax specified by the go tool.

Package collection seeks to provide an expressive and readable way of working with basic data structures in Go. As a former .NET developer, I deeply missed writing programs in the style of Linq. Doing so enables concurrent/ parallel reactive programs to be written in a snap. Go's functional nature enables us to have a very similar, if more verbose, experience. Take for example the scenario of printing the number of Go source files in a directory. Using this package, this takes only a few lines: A directory is a collection of filesystem entries, so we're able to iterate through them using the "Enumerate" function. From there, we filter on only file names that end with ".go". Finally, we print the number of entries that were encountered. This is a trivial example, but imagine building more elaborate pipelines. Maybe take advantage of the `SelectParallel` function which allows multiple goroutines to process a single transform at once, with their results being funnelled into the next phase of the pipeline. Suddenly, injecting new steps can be transparent.

Taken from $GOROOT/src/pkg/net/http/chunked needed to write https responses to client. Package goproxy provides a customizable HTTP proxy, supporting hijacking HTTPS connection. The intent of the proxy, is to be usable with reasonable amount of traffic yet, customizable and programable. The proxy itself is simply an `net/http` handler. Typical usage is Adding a header to each request For printing the content type of all incoming responses note that we used the ProxyCtx context variable here. It contains the request and the response (Req and Resp, Resp is nil if unavailable) of this specific client interaction with the proxy. To print the content type of all responses from a certain url, we'll add a ReqCondition to the OnResponse function: We can write the condition ourselves, conditions can be set on request and on response Caution! If you give a RespCondition to the OnRequest function, you'll get a run time panic! It doesn't make sense to read the response, if you still haven't got it! Finally, we have convenience function to throw a quick response we close the body of the original repsonse, and return a new 403 response with a short message. Example use cases: 1. https://github.com/elazarl/goproxy/tree/master/examples/goproxy-avgsize To measure the average size of an Html served in your site. One can ask all the QA team to access the website by a proxy, and the proxy will measure the average size of all text/html responses from your host. 2. [not yet implemented] All requests to your web servers should be directed through the proxy, when the proxy will detect html pieces sent as a response to AJAX request, it'll send a warning email. 3. https://github.com/elazarl/goproxy/blob/master/examples/goproxy-httpdump/ Generate a real traffic to your website by real users using through proxy. Record the traffic, and try it again for more real load testing. 4. https://github.com/elazarl/goproxy/tree/master/examples/goproxy-no-reddit-at-worktime Will allow browsing to reddit.com between 8:00am and 17:00pm 5. https://github.com/elazarl/goproxy/tree/master/examples/goproxy-jquery-version Will warn if multiple versions of jquery are used in the same domain. 6. https://github.com/elazarl/goproxy/blob/master/examples/goproxy-upside-down-ternet/ Modifies image files in an HTTP response via goproxy's image extension found in ext/.

Package validator implements value validations for structs and individual fields based on tags. It can also handle Cross-Field and Cross-Struct validation for nested structs and has the ability to dive into arrays and maps of any type. see more examples https://github.com/go-playground/validator/tree/master/_examples Validator is designed to be thread-safe and used as a singleton instance. It caches information about your struct and validations, in essence only parsing your validation tags once per struct type. Using multiple instances neglects the benefit of caching. The not thread-safe functions are explicitly marked as such in the documentation. Doing things this way is actually the way the standard library does, see the file.Open method here: The authors return type "error" to avoid the issue discussed in the following, where err is always != nil: Validator only InvalidValidationError for bad validation input, nil or ValidationErrors as type error; so, in your code all you need to do is check if the error returned is not nil, and if it's not check if error is InvalidValidationError ( if necessary, most of the time it isn't ) type cast it to type ValidationErrors like so err.(validator.ValidationErrors). Custom Validation functions can be added. Example: Cross-Field Validation can be done via the following tags: If, however, some custom cross-field validation is required, it can be done using a custom validation. Why not just have cross-fields validation tags (i.e. only eqcsfield and not eqfield)? The reason is efficiency. If you want to check a field within the same struct "eqfield" only has to find the field on the same struct (1 level). But, if we used "eqcsfield" it could be multiple levels down. Example: Multiple validators on a field will process in the order defined. Example: Bad Validator definitions are not handled by the library. Example: Baked In Cross-Field validation only compares fields on the same struct. If Cross-Field + Cross-Struct validation is needed you should implement your own custom validator. Comma (",") is the default separator of validation tags. If you wish to have a comma included within the parameter (i.e. excludesall=,) you will need to use the UTF-8 hex representation 0x2C, which is replaced in the code as a comma, so the above will become excludesall=0x2C. Pipe ("|") is the 'or' validation tags deparator. If you wish to have a pipe included within the parameter i.e. excludesall=| you will need to use the UTF-8 hex representation 0x7C, which is replaced in the code as a pipe, so the above will become excludesall=0x7C Here is a list of the current built in validators: Tells the validation to skip this struct field; this is particularly handy in ignoring embedded structs from being validated. (Usage: -) This is the 'or' operator allowing multiple validators to be used and accepted. (Usage: rgb|rgba) <-- this would allow either rgb or rgba colors to be accepted. This can also be combined with 'and' for example ( Usage: omitempty,rgb|rgba) When a field that is a nested struct is encountered, and contains this flag any validation on the nested struct will be run, but none of the nested struct fields will be validated. This is useful if inside of your program you know the struct will be valid, but need to verify it has been assigned. NOTE: only "required" and "omitempty" can be used on a struct itself. Same as structonly tag except that any struct level validations will not run. Allows conditional validation, for example if a field is not set with a value (Determined by the "required" validator) then other validation such as min or max won't run, but if a value is set validation will run. Allows to skip the validation if the value is nil (same as omitempty, but only for the nil-values). This tells the validator to dive into a slice, array or map and validate that level of the slice, array or map with the validation tags that follow. Multidimensional nesting is also supported, each level you wish to dive will require another dive tag. dive has some sub-tags, 'keys' & 'endkeys', please see the Keys & EndKeys section just below. Example #1 Example #2 Keys & EndKeys These are to be used together directly after the dive tag and tells the validator that anything between 'keys' and 'endkeys' applies to the keys of a map and not the values; think of it like the 'dive' tag, but for map keys instead of values. Multidimensional nesting is also supported, each level you wish to validate will require another 'keys' and 'endkeys' tag. These tags are only valid for maps. Example #1 Example #2 This validates that the value is not the data types default zero value. For numbers ensures value is not zero. For strings ensures value is not "". For booleans ensures value is not false. For slices, maps, pointers, interfaces, channels and functions ensures the value is not nil. For structs ensures value is not the zero value when using WithRequiredStructEnabled. The field under validation must be present and not empty only if all the other specified fields are equal to the value following the specified field. For strings ensures value is not "". For slices, maps, pointers, interfaces, channels and functions ensures the value is not nil. For structs ensures value is not the zero value. Examples: The field under validation must be present and not empty unless all the other specified fields are equal to the value following the specified field. For strings ensures value is not "". For slices, maps, pointers, interfaces, channels and functions ensures the value is not nil. For structs ensures value is not the zero value. Examples: The field under validation must be present and not empty only if any of the other specified fields are present. For strings ensures value is not "". For slices, maps, pointers, interfaces, channels and functions ensures the value is not nil. For structs ensures value is not the zero value. Examples: The field under validation must be present and not empty only if all of the other specified fields are present. For strings ensures value is not "". For slices, maps, pointers, interfaces, channels and functions ensures the value is not nil. For structs ensures value is not the zero value. Example: The field under validation must be present and not empty only when any of the other specified fields are not present. For strings ensures value is not "". For slices, maps, pointers, interfaces, channels and functions ensures the value is not nil. For structs ensures value is not the zero value. Examples: The field under validation must be present and not empty only when all of the other specified fields are not present. For strings ensures value is not "". For slices, maps, pointers, interfaces, channels and functions ensures the value is not nil. For structs ensures value is not the zero value. Example: The field under validation must not be present or not empty only if all the other specified fields are equal to the value following the specified field. For strings ensures value is not "". For slices, maps, pointers, interfaces, channels and functions ensures the value is not nil. For structs ensures value is not the zero value. Examples: The field under validation must not be present or empty unless all the other specified fields are equal to the value following the specified field. For strings ensures value is not "". For slices, maps, pointers, interfaces, channels and functions ensures the value is not nil. For structs ensures value is not the zero value. Examples: This validates that the value is the default value and is almost the opposite of required. For numbers, length will ensure that the value is equal to the parameter given. For strings, it checks that the string length is exactly that number of characters. For slices, arrays, and maps, validates the number of items. Example #1 Example #2 (time.Duration) For time.Duration, len will ensure that the value is equal to the duration given in the parameter. For numbers, max will ensure that the value is less than or equal to the parameter given. For strings, it checks that the string length is at most that number of characters. For slices, arrays, and maps, validates the number of items. Example #1 Example #2 (time.Duration) For time.Duration, max will ensure that the value is less than or equal to the duration given in the parameter. For numbers, min will ensure that the value is greater or equal to the parameter given. For strings, it checks that the string length is at least that number of characters. For slices, arrays, and maps, validates the number of items. Example #1 Example #2 (time.Duration) For time.Duration, min will ensure that the value is greater than or equal to the duration given in the parameter. For strings & numbers, eq will ensure that the value is equal to the parameter given. For slices, arrays, and maps, validates the number of items. Example #1 Example #2 (time.Duration) For time.Duration, eq will ensure that the value is equal to the duration given in the parameter. For strings & numbers, ne will ensure that the value is not equal to the parameter given. For slices, arrays, and maps, validates the number of items. Example #1 Example #2 (time.Duration) For time.Duration, ne will ensure that the value is not equal to the duration given in the parameter. For strings, ints, and uints, oneof will ensure that the value is one of the values in the parameter. The parameter should be a list of values separated by whitespace. Values may be strings or numbers. To match strings with spaces in them, include the target string between single quotes. Kind of like an 'enum'. Works the same as oneof but is case insensitive and therefore only accepts strings. For numbers, this will ensure that the value is greater than the parameter given. For strings, it checks that the string length is greater than that number of characters. For slices, arrays and maps it validates the number of items. Example #1 Example #2 (time.Time) For time.Time ensures the time value is greater than time.Now.UTC(). Example #3 (time.Duration) For time.Duration, gt will ensure that the value is greater than the duration given in the parameter. Same as 'min' above. Kept both to make terminology with 'len' easier. Example #1 Example #2 (time.Time) For time.Time ensures the time value is greater than or equal to time.Now.UTC(). Example #3 (time.Duration) For time.Duration, gte will ensure that the value is greater than or equal to the duration given in the parameter. For numbers, this will ensure that the value is less than the parameter given. For strings, it checks that the string length is less than that number of characters. For slices, arrays, and maps it validates the number of items. Example #1 Example #2 (time.Time) For time.Time ensures the time value is less than time.Now.UTC(). Example #3 (time.Duration) For time.Duration, lt will ensure that the value is less than the duration given in the parameter. Same as 'max' above. Kept both to make terminology with 'len' easier. Example #1 Example #2 (time.Time) For time.Time ensures the time value is less than or equal to time.Now.UTC(). Example #3 (time.Duration) For time.Duration, lte will ensure that the value is less than or equal to the duration given in the parameter. This will validate the field value against another fields value either within a struct or passed in field. Example #1: Example #2: Field Equals Another Field (relative) This does the same as eqfield except that it validates the field provided relative to the top level struct. This will validate the field value against another fields value either within a struct or passed in field. Examples: Field Does Not Equal Another Field (relative) This does the same as nefield except that it validates the field provided relative to the top level struct. Only valid for Numbers, time.Duration and time.Time types, this will validate the field value against another fields value either within a struct or passed in field. usage examples are for validation of a Start and End date: Example #1: Example #2: This does the same as gtfield except that it validates the field provided relative to the top level struct. Only valid for Numbers, time.Duration and time.Time types, this will validate the field value against another fields value either within a struct or passed in field. usage examples are for validation of a Start and End date: Example #1: Example #2: This does the same as gtefield except that it validates the field provided relative to the top level struct. Only valid for Numbers, time.Duration and time.Time types, this will validate the field value against another fields value either within a struct or passed in field. usage examples are for validation of a Start and End date: Example #1: Example #2: This does the same as ltfield except that it validates the field provided relative to the top level struct. Only valid for Numbers, time.Duration and time.Time types, this will validate the field value against another fields value either within a struct or passed in field. usage examples are for validation of a Start and End date: Example #1: Example #2: This does the same as ltefield except that it validates the field provided relative to the top level struct. This does the same as contains except for struct fields. It should only be used with string types. See the behavior of reflect.Value.String() for behavior on other types. This does the same as excludes except for struct fields. It should only be used with string types. See the behavior of reflect.Value.String() for behavior on other types. For arrays & slices, unique will ensure that there are no duplicates. For maps, unique will ensure that there are no duplicate values. For slices of struct, unique will ensure that there are no duplicate values in a field of the struct specified via a parameter. This validates that a string value contains ASCII alpha characters only This validates that a string value contains ASCII alphanumeric characters only This validates that a string value contains unicode alpha characters only This validates that a string value contains unicode alphanumeric characters only This validates that a string value can successfully be parsed into a boolean with strconv.ParseBool This validates that a string value contains number values only. For integers or float it returns true. This validates that a string value contains a basic numeric value. basic excludes exponents etc... for integers or float it returns true. This validates that a string value contains a valid hexadecimal. This validates that a string value contains a valid hex color including hashtag (#) This validates that a string value contains only lowercase characters. An empty string is not a valid lowercase string. This validates that a string value contains only uppercase characters. An empty string is not a valid uppercase string. This validates that a string value contains a valid rgb color This validates that a string value contains a valid rgba color This validates that a string value contains a valid hsl color This validates that a string value contains a valid hsla color This validates that a string value contains a valid E.164 Phone number https://en.wikipedia.org/wiki/E.164 (ex. +1123456789) This validates that a string value contains a valid email This may not conform to all possibilities of any rfc standard, but neither does any email provider accept all possibilities. This validates that a string value is valid JSON This validates that a string value is a valid JWT This validates that a string value contains a valid file path and that the file exists on the machine. This is done using os.Stat, which is a platform independent function. This validates that a string value contains a valid file path and that the file exists on the machine and is an image. This is done using os.Stat and github.com/gabriel-vasile/mimetype This validates that a string value contains a valid file path but does not validate the existence of that file. This is done using os.Stat, which is a platform independent function. This validates that a string value contains a valid url This will accept any url the golang request uri accepts but must contain a schema for example http:// or rtmp:// This validates that a string value contains a valid uri This will accept any uri the golang request uri accepts This validates that a string value contains a valid URN according to the RFC 2141 spec. This validates that a string value contains a valid bas324 value. Although an empty string is valid base32 this will report an empty string as an error, if you wish to accept an empty string as valid you can use this with the omitempty tag. This validates that a string value contains a valid base64 value. Although an empty string is valid base64 this will report an empty string as an error, if you wish to accept an empty string as valid you can use this with the omitempty tag. This validates that a string value contains a valid base64 URL safe value according the RFC4648 spec. Although an empty string is a valid base64 URL safe value, this will report an empty string as an error, if you wish to accept an empty string as valid you can use this with the omitempty tag. This validates that a string value contains a valid base64 URL safe value, but without = padding, according the RFC4648 spec, section 3.2. Although an empty string is a valid base64 URL safe value, this will report an empty string as an error, if you wish to accept an empty string as valid you can use this with the omitempty tag. This validates that a string value contains a valid bitcoin address. The format of the string is checked to ensure it matches one of the three formats P2PKH, P2SH and performs checksum validation. Bitcoin Bech32 Address (segwit) This validates that a string value contains a valid bitcoin Bech32 address as defined by bip-0173 (https://github.com/bitcoin/bips/blob/master/bip-0173.mediawiki) Special thanks to Pieter Wuille for providing reference implementations. This validates that a string value contains a valid ethereum address. The format of the string is checked to ensure it matches the standard Ethereum address format. This validates that a string value contains the substring value. This validates that a string value contains any Unicode code points in the substring value. This validates that a string value contains the supplied rune value. This validates that a string value does not contain the substring value. This validates that a string value does not contain any Unicode code points in the substring value. This validates that a string value does not contain the supplied rune value. This validates that a string value starts with the supplied string value This validates that a string value ends with the supplied string value This validates that a string value does not start with the supplied string value This validates that a string value does not end with the supplied string value This validates that a string value contains a valid isbn10 or isbn13 value. This validates that a string value contains a valid isbn10 value. This validates that a string value contains a valid isbn13 value. This validates that a string value contains a valid UUID. Uppercase UUID values will not pass - use `uuid_rfc4122` instead. This validates that a string value contains a valid version 3 UUID. Uppercase UUID values will not pass - use `uuid3_rfc4122` instead. This validates that a string value contains a valid version 4 UUID. Uppercase UUID values will not pass - use `uuid4_rfc4122` instead. This validates that a string value contains a valid version 5 UUID. Uppercase UUID values will not pass - use `uuid5_rfc4122` instead. This validates that a string value contains a valid ULID value. This validates that a string value contains only ASCII characters. NOTE: if the string is blank, this validates as true. This validates that a string value contains only printable ASCII characters. NOTE: if the string is blank, this validates as true. This validates that a string value contains one or more multibyte characters. NOTE: if the string is blank, this validates as true. This validates that a string value contains a valid DataURI. NOTE: this will also validate that the data portion is valid base64 This validates that a string value contains a valid latitude. This validates that a string value contains a valid longitude. This validates that a string value contains a valid U.S. Social Security Number. This validates that a string value contains a valid IP Address. This validates that a string value contains a valid v4 IP Address. This validates that a string value contains a valid v6 IP Address. This validates that a string value contains a valid CIDR Address. This validates that a string value contains a valid v4 CIDR Address. This validates that a string value contains a valid v6 CIDR Address. This validates that a string value contains a valid resolvable TCP Address. This validates that a string value contains a valid resolvable v4 TCP Address. This validates that a string value contains a valid resolvable v6 TCP Address. This validates that a string value contains a valid resolvable UDP Address. This validates that a string value contains a valid resolvable v4 UDP Address. This validates that a string value contains a valid resolvable v6 UDP Address. This validates that a string value contains a valid resolvable IP Address. This validates that a string value contains a valid resolvable v4 IP Address. This validates that a string value contains a valid resolvable v6 IP Address. This validates that a string value contains a valid Unix Address. This validates that a string value contains a valid MAC Address. Note: See Go's ParseMAC for accepted formats and types: This validates that a string value is a valid Hostname according to RFC 952 https://tools.ietf.org/html/rfc952 This validates that a string value is a valid Hostname according to RFC 1123 https://tools.ietf.org/html/rfc1123 Full Qualified Domain Name (FQDN) This validates that a string value contains a valid FQDN. This validates that a string value appears to be an HTML element tag including those described at https://developer.mozilla.org/en-US/docs/Web/HTML/Element This validates that a string value is a proper character reference in decimal or hexadecimal format This validates that a string value is percent-encoded (URL encoded) according to https://tools.ietf.org/html/rfc3986#section-2.1 This validates that a string value contains a valid directory and that it exists on the machine. This is done using os.Stat, which is a platform independent function. This validates that a string value contains a valid directory but does not validate the existence of that directory. This is done using os.Stat, which is a platform independent function. It is safest to suffix the string with os.PathSeparator if the directory may not exist at the time of validation. This validates that a string value contains a valid DNS hostname and port that can be used to validate fields typically passed to sockets and connections. This validates that a string value is a valid datetime based on the supplied datetime format. Supplied format must match the official Go time format layout as documented in https://golang.org/pkg/time/ This validates that a string value is a valid country code based on iso3166-1 alpha-2 standard. see: https://www.iso.org/iso-3166-country-codes.html This validates that a string value is a valid country code based on iso3166-1 alpha-3 standard. see: https://www.iso.org/iso-3166-country-codes.html This validates that a string value is a valid country code based on iso3166-1 alpha-numeric standard. see: https://www.iso.org/iso-3166-country-codes.html This validates that a string value is a valid BCP 47 language tag, as parsed by language.Parse. More information on https://pkg.go.dev/golang.org/x/text/language BIC (SWIFT code) This validates that a string value is a valid Business Identifier Code (SWIFT code), defined in ISO 9362. More information on https://www.iso.org/standard/60390.html This validates that a string value is a valid dns RFC 1035 label, defined in RFC 1035. More information on https://datatracker.ietf.org/doc/html/rfc1035 This validates that a string value is a valid time zone based on the time zone database present on the system. Although empty value and Local value are allowed by time.LoadLocation golang function, they are not allowed by this validator. More information on https://golang.org/pkg/time/#LoadLocation This validates that a string value is a valid semver version, defined in Semantic Versioning 2.0.0. More information on https://semver.org/ This validates that a string value is a valid cve id, defined in cve mitre. More information on https://cve.mitre.org/ This validates that a string value contains a valid credit card number using Luhn algorithm. This validates that a string or (u)int value contains a valid checksum using the Luhn algorithm. This validates that a string is a valid 24 character hexadecimal string or valid connection string. Example: This validates that a string value contains a valid cron expression. This validates that a string is valid for use with SpiceDb for the indicated purpose. If no purpose is given, a purpose of 'id' is assumed. Alias Validators and Tags NOTE: When returning an error, the tag returned in "FieldError" will be the alias tag unless the dive tag is part of the alias. Everything after the dive tag is not reported as the alias tag. Also, the "ActualTag" in the before case will be the actual tag within the alias that failed. Here is a list of the current built in alias tags: Validator notes: A collection of validation rules that are frequently needed but are more complex than the ones found in the baked in validators. A non standard validator must be registered manually like you would with your own custom validation functions. Example of registration and use: Here is a list of the current non standard validators: This package panics when bad input is provided, this is by design, bad code like that should not make it to production.

Package log4go provides level-based and highly configurable logging. This is inspired by the logging functionality in Java. Essentially, you create a Logger object and create output filters for it. You can send whatever you want to the Logger, and it will filter that based on your settings and send it to the outputs. This way, you can put as much debug code in your program as you want, and when you're done you can filter out the mundane messages so only the important ones show up. Utility functions are provided to make life easier. Here is some example code to get started: log := log4go.NewLogger() log.AddFilter("stdout", log4go.DEBUG, log4go.NewConsoleLogWriter()) log.AddFilter("log", log4go.FINE, log4go.NewFileLogWriter("example.log", true)) log.Info("The time is now: %s", time.LocalTime().Format("15:04:05 MST 2006/01/02")) The first two lines can be combined with the utility NewDefaultLogger: log := log4go.NewDefaultLogger(log4go.DEBUG) log.AddFilter("log", log4go.FINE, log4go.NewFileLogWriter("example.log", true)) log.Info("The time is now: %s", time.LocalTime().Format("15:04:05 MST 2006/01/02")) Usage notes: Changes from 2.0: Future work: (please let me know if you think I should work on any of these particularly)

Package bigmachine implements a vertically integrated stack for distributed computing in Go. Go programs written with bigmachine are transparently distributed across a number of machines as instantiated by the backend used. (Currently supported: EC2, local machines, unit tests.) Bigmachine clusters comprise a driver node and a number of bigmachine nodes (called "machines"). The driver node can create new machines and communicate with them; machines can call each other. On startup, a bigmachine program calls driver.Start. Driver.Start configures a bigmachine instance based on a set of standard flags and then starts it. (Users desiring a lower-level API can use bigmachine.Start directly.) When the program is run, driver.Start returns immediately: the program can then interact with the returned bigmachine B to create new machines, define services on those machines, and invoke methods on those services. Bigmachine bootstraps machines by running the same binary, but in these runs, driver.Start never returns; instead it launches a server to handle calls from the driver program and other machines. A machine is started by (*B).Start. Machines must be configured with at least one service: Users may then invoke methods on the services provided by the returned machine. A services's methods can be invoked so long as they are of the form: See package github.com/grailbio/bigmachine/rpc for more details. Methods are named by the sevice and method name, separated by a dot ('.'), e.g.: "MyService.MyMethod": Since service instances must be serialized so that they can be transmitted to the remote machine, and because we do not know the service types a priori, any type that can appear as a service must be registered with gob. This is usually done in an init function in the package that declares type: A bigmachine program attempts to appear and act like a single program: The driver program maintains keepalives to all of its machines. Once this is no longer maintained (e.g., because the driver finished, or crashed, or lost connectivity), the machines become idle and shut down. A service is any Go value that implements methods of the form given above. Services are instantiated by the user and registered with bigmachine. When a service is registered, bigmachine will also invoke an initialization method on the service if it exists. Per-machine initialization can be performed by this method.The form of the method is: If a non-nil error is returned, the machine is considered failed.

Package spanner provides a client for reading and writing to Cloud Spanner databases. See the packages under admin for clients that operate on databases and instances. Note: This package is in beta. Some backwards-incompatible changes may occur. See https://cloud.google.com/spanner/docs/getting-started/go/ for an introduction to Cloud Spanner and additional help on using this API. See https://godoc.org/cloud.google.com/go for authentication, timeouts, connection pooling and similar aspects of this package. To start working with this package, create a client that refers to the database of interest: Remember to close the client after use to free up the sessions in the session pool. Two Client methods, Apply and Single, work well for simple reads and writes. As a quick introduction, here we write a new row to the database and read it back: All the methods used above are discussed in more detail below. Every Cloud Spanner row has a unique key, composed of one or more columns. Construct keys with a literal of type Key: The keys of a Cloud Spanner table are ordered. You can specify ranges of keys using the KeyRange type: By default, a KeyRange includes its start key but not its end key. Use the Kind field to specify other boundary conditions: A KeySet represents a set of keys. A single Key or KeyRange can act as a KeySet. Use the KeySets function to build the union of several KeySets: AllKeys returns a KeySet that refers to all the keys in a table: All Cloud Spanner reads and writes occur inside transactions. There are two types of transactions, read-only and read-write. Read-only transactions cannot change the database, do not acquire locks, and may access either the current database state or states in the past. Read-write transactions can read the database before writing to it, and always apply to the most recent database state. The simplest and fastest transaction is a ReadOnlyTransaction that supports a single read operation. Use Client.Single to create such a transaction. You can chain the call to Single with a call to a Read method. When you only want one row whose key you know, use ReadRow. Provide the table name, key, and the columns you want to read: Read multiple rows with the Read method. It takes a table name, KeySet, and list of columns: Read returns a RowIterator. You can call the Do method on the iterator and pass a callback: RowIterator also follows the standard pattern for the Google Cloud Client Libraries: Always call Stop when you finish using an iterator this way, whether or not you iterate to the end. (Failing to call Stop could lead you to exhaust the database's session quota.) To read rows with an index, use ReadUsingIndex. The most general form of reading uses SQL statements. Construct a Statement with NewStatement, setting any parameters using the Statement's Params map: You can also construct a Statement directly with a struct literal, providing your own map of parameters. Use the Query method to run the statement and obtain an iterator: Once you have a Row, via an iterator or a call to ReadRow, you can extract column values in several ways. Pass in a pointer to a Go variable of the appropriate type when you extract a value. You can extract by column position or name: You can extract all the columns at once: Or you can define a Go struct that corresponds to your columns, and extract into that: For Cloud Spanner columns that may contain NULL, use one of the NullXXX types, like NullString: To perform more than one read in a transaction, use ReadOnlyTransaction: You must call Close when you are done with the transaction. Cloud Spanner read-only transactions conceptually perform all their reads at a single moment in time, called the transaction's read timestamp. Once a read has started, you can call ReadOnlyTransaction's Timestamp method to obtain the read timestamp. By default, a transaction will pick the most recent time (a time where all previously committed transactions are visible) for its reads. This provides the freshest data, but may involve some delay. You can often get a quicker response if you are willing to tolerate "stale" data. You can control the read timestamp selected by a transaction by calling the WithTimestampBound method on the transaction before using it. For example, to perform a query on data that is at most one minute stale, use See the documentation of TimestampBound for more details. To write values to a Cloud Spanner database, construct a Mutation. The spanner package has functions for inserting, updating and deleting rows. Except for the Delete methods, which take a Key or KeyRange, each mutation-building function comes in three varieties. One takes lists of columns and values along with the table name: One takes a map from column names to values: And the third accepts a struct value, and determines the columns from the struct field names: To apply a list of mutations to the database, use Apply: If you need to read before writing in a single transaction, use a ReadWriteTransaction. ReadWriteTransactions may abort and need to be retried. You pass in a function to ReadWriteTransaction, and the client will handle the retries automatically. Use the transaction's BufferWrite method to buffer mutations, which will all be executed at the end of the transaction: Spanner supports DML statements like INSERT, UPDATE and DELETE. Use ReadWriteTransaction.Update to run DML statements. It returns the number of rows affected. (You can call use ReadWriteTransaction.Query with a DML statement. The first call to Next on the resulting RowIterator will return iterator.Done, and the RowCount field of the iterator will hold the number of affected rows.) For large databases, it may be more efficient to partition the DML statement. Use client.PartitionedUpdate to run a DML statement in this way. Not all DML statements can be partitioned. This client has been instrumented to use OpenCensus tracing (http://opencensus.io). To enable tracing, see "Enabling Tracing for a Program" at https://godoc.org/go.opencensus.io/trace. OpenCensus tracing requires Go 1.8 or higher.

Package tcell provides a lower-level, portable API for building programs that interact with terminals or consoles. It works with both common (and many uncommon!) terminals or terminal emulators, and Windows console implementations. It provides support for up to 256 colors, text attributes, and box drawing elements. A database of terminals built from a real terminfo database is provided, along with code to generate new database entries. Tcell offers very rich support for mice, dependent upon the terminal of course. (Windows, XTerm, and iTerm 2 are known to work very well.) If the environment is not Unicode by default, such as an ISO8859 based locale or GB18030, Tcell can convert input and output, so that your terminal can operate in whatever locale is most convenient, while the application program can just assume "everything is UTF-8". Reasonable defaults are used for updating characters to something suitable for display. Unicode box drawing characters will be converted to use the alternate character set of your terminal, if native conversions are not available. If no ACS is available, then some ASCII fallbacks will be used. Note that support for non-UTF-8 locales (other than C) must be enabled by the application using RegisterEncoding() -- we don't have them all enabled by default to avoid bloating the application unneccessarily. (These days UTF-8 is good enough for almost everyone, and nobody should be using legacy locales anymore.) Also, actual glyphs for various code point will only be displayed if your terminal or emulator (or the font the emulator is using) supports them. A rich set of keycodes is supported, with support for up to 65 function keys, and various other special keys.

Package glog implements logging analogous to the Google-internal C++ INFO/ERROR/V setup. It provides functions Info, Warning, Error, Fatal, plus formatting variants such as Infof. It also provides V-style logging controlled by the -v and -vmodule=file=2 flags. Basic examples: See the documentation for the V function for an explanation of these examples: Log output is buffered and written periodically using Flush. Programs should call Flush before exiting to guarantee all log output is written. By default, all log statements write to files in a temporary directory. This package provides several flags that modify this behavior. As a result, flag.Parse must be called before any logging is done.

Package glog implements logging analogous to the Google-internal C++ INFO/ERROR/V setup. It provides functions Info, Warning, Error, Fatal, plus formatting variants such as Infof. It also provides V-style logging controlled by the -v and -vmodule=file=2 flags. Basic examples: See the documentation for the V function for an explanation of these examples: Log output is buffered and written periodically using Flush. Programs should call Flush before exiting to guarantee all log output is written. By default, all log statements write to files in a temporary directory. This package provides several flags that modify this behavior. As a result, flag.Parse must be called before any logging is done.

Package glog implements logging analogous to the Google-internal C++ INFO/ERROR/V setup. It provides functions Info, Warning, Error, Fatal, plus formatting variants such as Infof. It also provides V-style logging controlled by the -v and -vmodule=file=2 flags. Basic examples: See the documentation for the V function for an explanation of these examples: Log output is buffered and written periodically using Flush. Programs should call Flush before exiting to guarantee all log output is written. By default, all log statements write to files in a temporary directory. This package provides several flags that modify this behavior. As a result, flag.Parse must be called before any logging is done.

Package writ implements a flexible option parser with thorough test coverage. It's meant to be simple and "just work". Applications using writ look and behave similar to common GNU command-line applications, making them comfortable for end-users. Writ implements option decoding with GNU getopt_long conventions. All long and short-form option variations are supported: --with-x, --name Sam, --day=Friday, -i FILE, -vvv, etc. Help output generation is supported using text/template. The default template can be overriden with a custom template. Writ uses the Command and Option types to represent available options and subcommands. Input arguments are decoded with Command.Decode(). For convenience, the New() function can parse an input struct into a Command with Options that represent the input struct's fields. It uses struct field tags to control the behavior. The resulting Command's Decode() method updates the struct's fields in-place when option arguments are decoded. Alternatively, Commands and Options may be created directly. All fields on these types are exported. Options are specified via the "option" and "flag" struct tags. Both represent options, but fields marked "option" take arguments, whereas fields marked "flag" do not. Every Option must have an OptionDecoder. Writ provides decoders for most basic types, as well as some convenience types. See the NewOptionDecoder() function docs for details. New() parses an input struct to build a top-level Command. Subcommands are supported by using the "command" field tag. Fields marked with "command" must be of struct type, and are parsed the same way as top-level commands. Writ provides methods for generating help output. Command.WriteHelp() generates help content and writes to a given io.Writer. Command.ExitHelp() writes help content to stdout or stderr and terminates the program. Writ uses a template to generate the help content. The default template mimics --help output for common GNU programs. See the documentation of the Help type for more details. The New() function recognizes the following combinations of field tags: If both "default" and "env" are specified for an option field, the environment variable is consulted first. If the environment variable is present and decodes without error, that value is used. Otherwise, the value for the "default" tag is used. Values specified via parsed arguments take precedence over both types of defaults. This example uses writ.New() to build a command from the Greeter's struct fields. The resulting *writ.Command decodes and updates the Greeter's fields in-place. The Command.ExitHelp() method is used to display help content if --help is specified, or if invalid input arguments are received. This example demonstrates some of the convenience features offered by writ. It uses writ's support for io types and default values to ensure the Input and Output fields are initialized. These default to stdin and stdout due to the default:"-" field tags. The user may specify -i or -o to read from or write to a file. Similarly, the Replacements map is initialized with key=value pairs for every -r/--replace option the user specifies. This example demonstrates explicit Command and Option creation, along with explicit option grouping. It checks the host platform and dynamically adds a --bootloader option if the example is run on Linux. The same result could be achieved by using writ.New() to construct a Command, and then adding the platform-specific option to the resulting Command directly. This example demonstrates subcommands in a busybox style. There's no requirement that subcommands implement the Run() method shown here. It's just an example of how subcommands might be implemented.

Package fortuna implements the Fortuna random number generator by Niels Ferguson and Bruce Schneier. Fortuna is a cryptographically strong pseudo-random number generator; typical use cases include generation of keys in cryptographic ciphers and session tokens for web apps. The homepage of this package is at http://www.seehuhn.de/pages/fortuna . Please send any comments or bug reports to the program's author, Jochen Voss <voss@seehuhn.de>. The Fortuna random number generator consists of two parts: The accumulator collects caller-provided randomness (e.g. timings between the user's key presses). This randomness is then used to seed a pseudo random number generator. During operation, the randomness from the accumulator is also used to periodically reseed the generator, thus allowing to recover from limited compromises of the generator's state. The accumulator and the generator are described in separate sections, below. The usual way to use the Fortuna random number generator is by creating an object of type Accumulator. A new Accumulator can be allocated using the NewRNG() function: The argument seedFileName is the name of a file where a small amount of randomness can be stored between runs of the program. The program must be able to both read and write this file, and the contents must be kept confidential. If the seedFileName argument equals the empty string "", no entropy is stored between runs. In this case, the initial seed is only based on the current time of day, the current user name, the list of currently installed network interfaces, and output of the system random number generator. Not using a seed file can lead to more predictable output in the initial period after the generator has been created; a seed file must be used in security sensitive applications. If a seed file is used, the Accumulator must be closed using the Close() method after use. Randomness can be extracted from the Accumulator using the RandomData() and Read() methods. For example, a slice of 16 random bytes can be obtained using the following command: The Accumulator uses 32 entropy pools to collect randomness from the environment. The use of external entropy helps to recover from situations where an attacker obtained (partial) knowledge of the generator state. Any program using the Fortuna generator should continuously collect random/unpredictable data and should submit this data to the Accumulator. For example, code like the following could be used to submit the times between requests in a web-server: The Generator class provides a pseudo random number generator which forms the basis of the Accumulator described above. New instances of the Fortuna pseudo random number generator can be created using the NewGenerator() function. The argument newCipher should normally be aes.NewCipher from the crypto/aes package, but the Serpent or Twofish ciphers can also be used: The generator can be seeded using the Seed() or Reseed() methods: The method .Seed() should be used if reproducible output is required, whereas .Reseed() can be used to add entropy in order to achieve less predictable output. Uniformly distributed random bytes can then be extracted using the .PseudoRandomData() method: Generator implements the rand.Source interface and thus the functions from the math/rand package can be used to obtain pseudo random samples from more complicated distributions.

Package szTest helpers. Golang testing utility. Copyright (C) 2023 Leslie Dancsecs This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program. If not, see <https://www.gnu.org/licenses/>. Implements some general go testing helper functions to provide for cleaner more readable tests as well as automatic diffs of unexpected results. In addition to providing general tests it also provides builtin io interfaces that can be used to simulate io errors for code tests. Finally it provides for the capturing of logs and standard output streams with automatic diffs.

Package spanner provides a client for reading and writing to Cloud Spanner databases. See the packages under admin for clients that operate on databases and instances. Note: This package is in beta. Some backwards-incompatible changes may occur. See https://cloud.google.com/spanner/docs/getting-started/go/ for an introduction to Cloud Spanner and additional help on using this API. See https://godoc.org/cloud.google.com/go for authentication, timeouts, connection pooling and similar aspects of this package. To start working with this package, create a client that refers to the database of interest: Remember to close the client after use to free up the sessions in the session pool. Two Client methods, Apply and Single, work well for simple reads and writes. As a quick introduction, here we write a new row to the database and read it back: All the methods used above are discussed in more detail below. Every Cloud Spanner row has a unique key, composed of one or more columns. Construct keys with a literal of type Key: The keys of a Cloud Spanner table are ordered. You can specify ranges of keys using the KeyRange type: By default, a KeyRange includes its start key but not its end key. Use the Kind field to specify other boundary conditions: A KeySet represents a set of keys. A single Key or KeyRange can act as a KeySet. Use the KeySets function to build the union of several KeySets: AllKeys returns a KeySet that refers to all the keys in a table: All Cloud Spanner reads and writes occur inside transactions. There are two types of transactions, read-only and read-write. Read-only transactions cannot change the database, do not acquire locks, and may access either the current database state or states in the past. Read-write transactions can read the database before writing to it, and always apply to the most recent database state. The simplest and fastest transaction is a ReadOnlyTransaction that supports a single read operation. Use Client.Single to create such a transaction. You can chain the call to Single with a call to a Read method. When you only want one row whose key you know, use ReadRow. Provide the table name, key, and the columns you want to read: Read multiple rows with the Read method. It takes a table name, KeySet, and list of columns: Read returns a RowIterator. You can call the Do method on the iterator and pass a callback: RowIterator also follows the standard pattern for the Google Cloud Client Libraries: Always call Stop when you finish using an iterator this way, whether or not you iterate to the end. (Failing to call Stop could lead you to exhaust the database's session quota.) To read rows with an index, use ReadUsingIndex. The most general form of reading uses SQL statements. Construct a Statement with NewStatement, setting any parameters using the Statement's Params map: You can also construct a Statement directly with a struct literal, providing your own map of parameters. Use the Query method to run the statement and obtain an iterator: Once you have a Row, via an iterator or a call to ReadRow, you can extract column values in several ways. Pass in a pointer to a Go variable of the appropriate type when you extract a value. You can extract by column position or name: You can extract all the columns at once: Or you can define a Go struct that corresponds to your columns, and extract into that: For Cloud Spanner columns that may contain NULL, use one of the NullXXX types, like NullString: To perform more than one read in a transaction, use ReadOnlyTransaction: You must call Close when you are done with the transaction. Cloud Spanner read-only transactions conceptually perform all their reads at a single moment in time, called the transaction's read timestamp. Once a read has started, you can call ReadOnlyTransaction's Timestamp method to obtain the read timestamp. By default, a transaction will pick the most recent time (a time where all previously committed transactions are visible) for its reads. This provides the freshest data, but may involve some delay. You can often get a quicker response if you are willing to tolerate "stale" data. You can control the read timestamp selected by a transaction by calling the WithTimestampBound method on the transaction before using it. For example, to perform a query on data that is at most one minute stale, use See the documentation of TimestampBound for more details. To write values to a Cloud Spanner database, construct a Mutation. The spanner package has functions for inserting, updating and deleting rows. Except for the Delete methods, which take a Key or KeyRange, each mutation-building function comes in three varieties. One takes lists of columns and values along with the table name: One takes a map from column names to values: And the third accepts a struct value, and determines the columns from the struct field names: To apply a list of mutations to the database, use Apply: If you need to read before writing in a single transaction, use a ReadWriteTransaction. ReadWriteTransactions may abort and need to be retried. You pass in a function to ReadWriteTransaction, and the client will handle the retries automatically. Use the transaction's BufferWrite method to buffer mutations, which will all be executed at the end of the transaction: Spanner supports DML statements like INSERT, UPDATE and DELETE. Use ReadWriteTransaction.Update to run DML statements. It returns the number of rows affected. (You can call use ReadWriteTransaction.Query with a DML statement. The first call to Next on the resulting RowIterator will return iterator.Done, and the RowCount field of the iterator will hold the number of affected rows.) For large databases, it may be more efficient to partition the DML statement. Use client.PartitionedUpdate to run a DML statement in this way. Not all DML statements can be partitioned. This client has been instrumented to use OpenCensus tracing (http://opencensus.io). To enable tracing, see "Enabling Tracing for a Program" at https://godoc.org/go.opencensus.io/trace. OpenCensus tracing requires Go 1.8 or higher.

Package ki provides the base element of Goki Trees: Ki = Tree in Japanese, and "Key" in English -- powerful tree structures supporting scenegraphs, programs, parsing, etc. The Node struct that implements the Ki interface, which can be used as an embedded type (or a struct field) in other structs to provide core tree functionality, including: Parent / Child Tree structure -- each Node can ONLY have one parent. Node struct's can also have Node fields -- these are functionally like fixed auto-named children. Paths for locating Nodes within the hierarchy -- key for many use-cases, including ability to convert pointers to/from strings for IO and robust deep copy and move functions. The path separator is / for children and . for fields. Apply a function across nodes up or down a tree (natural "me first", breadth-first, depth-first) -- very flexible for tree walking. Generalized I/O -- can Save and Load the Tree as JSON, XML, etc -- including pointers which are saved using paths and automatically cached-out after loading -- enums also bidirectionally convertable to strings using enum type registry in kit package. Robust deep copy, clone, move of nodes. Signal sending and receiving between Nodes (simlar to Qt Signals / Slots) -- setup connections once and then emit signals to all receivers when relevant event happens. Robust state updating -- wrap updates in UpdateStart / End, and signals are blocked until the final end, at the highest affected level in the tree, at which point a single update signal is sent -- automatically gives the minimal update. Properties (as a string-keyed map) with property inheritance, including type-level properties via kit type registry. In general, the names of the children of a given node should all be unique. The following functions defined in ki package can be used: * UniqueNameCheck(node) to check for unique names on node if uncertain. * UniqueNameCheckAll(node) to check entire tree under given node. * UniquifyNames(node) to add a suffix to name to ensure uniqueness. * UniquifyNamesAll(node) to to uniquify all names in entire tree. The Ki interface is designed to support virtual method calling in Go and is only intended to be implemented once, by the ki.Node type (as opposed to interfaces that are used for hiding multiple different implementations of a common concept). Thus, all of the fields in ki.Node are exported (have captital names), to be accessed directly in types that embed and extend the ki.Node. The Ki interface has the "formal" name (e.g., Children) while the Node has the "nickname" (e.g., Kids). See the Naming Conventions on the Goki Wiki for more details. Each Node stores the Ki interface version of itself, as This() / Ths which enables full virtual function calling by calling the method on that interface instead of directly on the receiver Node itself. This requires proper initialization via Init method of the Ki interface.

Package glog implements logging analogous to the Google-internal C++ INFO/ERROR/V setup. It provides functions that have a name matched by regex: If Context is present, function takes context.Context argument. The context is used to pass through the Trace Context to log sinks that can make use of it. It is recommended to use the context variant of the functions over the non-context variants if a context is available to make sure the Trace Contexts are present in logs. If Depth is present, this function calls log from a different depth in the call stack. This enables a callee to emit logs that use the callsite information of its caller or any other callers in the stack. When depth == 0, the original callee's line information is emitted. When depth > 0, depth frames are skipped in the call stack and the final frame is treated like the original callee to Info. If 'f' is present, function formats according to a format specifier. This package also provides V-style logging controlled by the -v and -vmodule=file=2 flags. Basic examples: See the documentation for the V function for an explanation of these examples: Log output is buffered and written periodically using Flush. Programs should call Flush before exiting to guarantee all log output is written. By default, all log statements write to files in a temporary directory. This package provides several flags that modify this behavior. As a result, flag.Parse must be called before any logging is done. Other flags provide aids to debugging.

Elvish is a cross-platform shell, supporting Linux, BSDs and Windows. It features an expressive programming language, with features like namespacing and anonymous functions, and a fully programmable user interface with friendly defaults. It is suitable for both interactive use and scripting.

Package http is a fork of stdlib's net/http that provides HTTP client and server implementations that are compatible with alternative TLS libraries such as github.com/refraction-networking/utls. See https://github.com/ooni/oohttp for more information on how to use this package and which are its limitations. Get, Head, Post, and PostForm make HTTP (or HTTPS) requests: The caller must close the response body when finished with it: For control over HTTP client headers, redirect policy, and other settings, create a Client: For control over proxies, TLS configuration, keep-alives, compression, and other settings, create a Transport: Clients and Transports are safe for concurrent use by multiple goroutines and for efficiency should only be created once and re-used. ListenAndServe starts an HTTP server with a given address and handler. The handler is usually nil, which means to use DefaultServeMux. Handle and HandleFunc add handlers to DefaultServeMux: More control over the server's behavior is available by creating a custom Server: Starting with Go 1.6, the http package has transparent support for the HTTP/2 protocol when using HTTPS. Programs that must disable HTTP/2 can do so by setting [Transport.TLSNextProto] (for clients) or [Server.TLSNextProto] (for servers) to a non-nil, empty map. Alternatively, the following GODEBUG settings are currently supported: Please report any issues before disabling HTTP/2 support: https://golang.org/s/http2bug The http package's Transport and Server both automatically enable HTTP/2 support for simple configurations. To enable HTTP/2 for more complex configurations, to use lower-level HTTP/2 features, or to use a newer version of Go's http2 package, import "golang.org/x/net/http2" directly and use its ConfigureTransport and/or ConfigureServer functions. Manually configuring HTTP/2 via the golang.org/x/net/http2 package takes precedence over the net/http package's built-in HTTP/2 support.

Package log4go provides level-based and highly configurable logging. This is inspired by the logging functionality in Java. Essentially, you create a Logger object and create output filters for it. You can send whatever you want to the Logger, and it will filter that based on your settings and send it to the outputs. This way, you can put as much debug code in your program as you want, and when you're done you can filter out the mundane messages so only the important ones show up. Utility functions are provided to make life easier. Here is some example code to get started: log := log4go.NewLogger() log.AddFilter("stdout", log4go.DEBUG, log4go.NewConsoleLogWriter()) log.AddFilter("log", log4go.FINE, log4go.NewFileLogWriter("example.log", true)) log.Info("The time is now: %s", time.LocalTime().Format("15:04:05 MST 2006/01/02")) The first two lines can be combined with the utility NewDefaultLogger: log := log4go.NewDefaultLogger(log4go.DEBUG) log.AddFilter("log", log4go.FINE, log4go.NewFileLogWriter("example.log", true)) log.Info("The time is now: %s", time.LocalTime().Format("15:04:05 MST 2006/01/02")) Usage notes: Changes from 2.0: Future work: (please let me know if you think I should work on any of these particularly)