Transportation API

Package apns provide a Apple Push Notification service provider. Apple Push Notification service (APNs) is the centerpiece of the remote notifications feature. It is a robust and highly efficient service for propagating information to iOS (and, indirectly, watchOS), tvOS, and macOS devices. On initial activation, a device establishes an accredited and encrypted IP connection with APNs and receives notifications over this persistent connection. If a notification for an app arrives when that app is not running, the device alerts the user that the app has data waiting for it. You provide your own server to generate remote notifications for the users of your app. This server, known as the provider, has three main responsibilities. It: For each notification, the provider: On receiving the HTTP/2 request, APNs delivers the notification payload to your app on the user's device. Apple Push Notification service includes a default Quality of Service (QoS) component that performs a store-and-forward function. If APNs attempts to deliver a notification but the destination device is offline, APNs stores the notification for a limited period of time and delivers it to the device when the device becomes available. This mechanism stores only one recent notification per device, per app: if you send multiple notifications while a device is offline, a new notification causes the previous notification to be discarded. If a device remains offline for a long time, all notifications that were being stored for it are discarded; when the device goes back online, none of the notifications are displayed. When a device is online, all the notifications you send are delivered and available to the user. However, you can avoid showing duplicate notifications by employing a collapse identifier across multiple, identical notifications. The APNs request header key for the collapse identifier is "apns-collapse-id". For example, a news service that sends the same headline twice in a row could employ the same collapse identifier for both push notification requests. APNs would then take care of coalescing these requests into a single notification for delivery to a device. To ensure secure communication, APNs servers employ connection certificates, certification authority (CA) certificates, and cryptographic keys (private and public) to validate connections to, and identities of, providers and devices. APNs regulates the entry points between providers and devices using two levels of trust: connection trust and device token trust. Connection trust establishes certainty that APNs is connected to an authorized provider, owned by a company that Apple has agreed to deliver notifications for. You must take steps to ensure connection trust exists between your provider servers and APNs. APNs also uses connection trust with each device to ensure the legitimacy of the device. Connection trust with the device is handled automatically by APNs. Device token trust ensures that notifications are routed only between legitimate start and end points. A device token is an opaque, unique identifier assigned to a specific app on a specific device. Each app instance receives its unique token when it registers with APNs. The app must share this token with its provider, to allow the provider to employ the token when communicating with APNs. Each notification that your provider sends to APNs must include the device token, which ensures that the notification is delivered only to the app-device combination for which it is intended. Important: To protect user privacy, do not attempt to use a device token to identify a device. Device tokens can change after updating the operating system, and always change when a device's data and settings are erased. Whenever the system delivers a device token to an instance of your app, the app must forward it to your provider servers to allow further push notifications to the device. A provider using the HTTP/2-based APNs Provider API can use JSON web tokens (JWT) to validate the provider's connection with APNs. In this scheme, the provider does not require a certificate-plus-private key to establish connection. Instead, you provision a public key to be retained by Apple, and a private key which you retain and protect. Your providers then use your private key to generate and sign JWT authentication tokens. Each of your push requests must include an authentication token. Important: To establish TLS sessions with APNs, you must ensure that a GeoTrust Global CA root certificate is installed on each of your providers. You can download this certificate from the GeoTrust Root Certificates website: https://www.geotrust.com/resources/root-certificates/. The HTTP/2-based provider connection is valid for delivery to one specific app, identified by the topic (the app bundle ID) specified in the certificate. Depending on how you configure and provision your APNs Transport Layer Security (TLS) certificate, the trusted connection can also be valid for delivery of remote notifications to other items associated with your app, including Apple Watch complications and voice-over-Internet Protocol (VoIP) services. APNs delivers these notifications even when those items are running in the background. APNs maintains a certificate revocation list; if a provider's certificate is on the revocation list, APNs can revoke provider trust (that is, APNs can refuse the TLS initiation connection).

Package yext provides bindings for Yext Location Cloud APIs. For full documentation visit http://developer.yext.com/docs/api-reference/ Create an authenticated client (requires an API key) List all locations Fetch a single location Create a new location (see full documentation for required fields) Edit an existing location The behavior of the API client can be controlled with a Config instance. The Config type exposes chainable utility methods to make construction simpler. By default, clients will retry API requests up to 3 times in the case of non-4xx errors including HTTP transport, 5xx responses, etc. This can be modified via Config: In order to support partial object updates, many of the struct attributes are represented as pointers in order to differentiate between "not-present" and "zero-valued". Helpers are provided to make it easier to work with the pointers: In addition, accessors are provided to make extracting data from the model objects simpler: Errors returned from the API are surfaced as Errors objects. The Errors object is comprised of a list of errors, each with a Message, Code, and Type. A full list of expected errors can be found here: http://developer.yext.com/support/error-messages/ Most functions that interact with the API will return at least two parameters - a yext.Response object and an error. Response contains a Meta substructure that in turn has a UUID and Errors attribute. The UUID can be used to look up individual requests in the developer.yext.com portal, useful for debugging requests. Most of the functionality within the API is exposed via domain-specific services available under the `Client` object. For example, if you are interacting with Locations, use the Client instance's LocationService. If you need to interact with Users, you'd use the UserService. Each service provides a set of common data-access functions that you can use to interact with objects under the service's domain. Where appropriate, services will expose additional, domain-specific functionality.

Package ngrok makes it easy to work with the ngrok API from Go. The package is fully code generated and should always be up to date with the latest ngrok API. Full documentation of the ngrok API can be found at: https://ngrok.com/docs/api This package follows the best practices outlined for Go modules. All releases are tagged and any breaking changes will be reflected as a new major version. You should only import this package for production applications by pointing at a stable tagged version. The following example code demonstrates typical initialization and usage of the package to make an API call: API client configuration and all of the datatypes exchanged by the API are defined in this base package. There are subpackages for every API service and a Client type defined in those packages with methods to interact with that API service. It's usually easiest to find the subpackage of the service you want to work with and begin consulting the documentation there. It is recommended to construct the service-specific clients once at initialization time. The ClientConfig object in the root package supports functional options for configuration. The most common option to use is `WithHTTPClient()` which allows the caller to specify a different net/http.Client object. This allows the caller full customization over the transport if needed for use with proxies, custom TLS setups, observability and tracing, etc. Some arguments to methods in the ngrok API are optional and must be meaningfully distinguished from zero values, especially in Update() methods. This allows the API to distinguish between choosing not to update a value vs. setting it to zero or the empty string. For these arguments, ngrok follows the industry standard practice of using pointers to the primitive types and providing convenince functions like ngrok.String() and ngrok.Bool() for the caller to wrap literals as pointer values. For example: All List methods in the ngrok API are paged. This package abstracts that problem away from you by returning an iterator from any List API call. As you advance the iterator it will transparently fetch new pages of values for you behind the scenes. Note that the context supplied to the initial List() call will be used for all subsequent page fetches so it must be long enough to work through the entire list. Here's an example of paging through all of the TLS certificates on your account. Note that you must check for an error after Next() returns false to determine if the iterator failed to fetch the next page of results. All errors returned by the ngrok API are returned as structured payloads for easy error handling. Most non-networking errors returned by API calls in this package will be an ngrok.Error type. The ngrok.Error type exposes important metadata that will help you handle errors. Specifically it includes the HTTP status code of any failed operation as well as an error code value that uniquely identifies the failure condition. There are two helper functions that will make error handling easy: IsNotFound and IsErrorCode. IsNotFound helps identify the common case of accessing an API resource that no longer exists: IsErrorCode helps you identify specific ngrok errors by their unique ngrok error code. All ngrok error codes are documented at https://ngrok.com/docs/errors To check for a specific error condition, you would structure your code like the following example: All ngrok datatypes in this package define String() and GoString() methods so that they can be formatted into strings in helpful representations. The GoString() method is defined to pretty-print an object for debugging purposes with the "%#v" formatting verb.

muxado implements a general purpose stream-multiplexing protocol. muxado allows clients applications to multiplex any io.ReadWriteCloser (like a net.Conn) into multiple, independent full-duplex streams. muxado is a useful protocol for any two communicating processes. It is an excellent base protocol for implementing lightweight RPC. It eliminates the need for custom async/pipeling code from your peers in order to support multiple simultaneous inflight requests between peers. For the same reason, it also eliminates the need to build connection pools for your clients. It enables servers to initiate streams to clients without building any NAT traversal. muxado can also yield performance improvements (especially latency) for protocols that require rapidly opening many concurrent connections. Here's an example client which responds to simple JSON requests from a server. Maybe the client wants to make a request to the server instead of just responding. This is easy as well: muxado defines the following terms for clarity of the documentation: A "Transport" is an underlying stream (typically TCP) that is multiplexed by sending frames between muxado peers over this transport. A "Stream" is any of the full-duplex byte-streams multiplexed over the transport A "Session" is two peers running the muxado protocol over a single transport muxado's design is influenced heavily by the framing layer of HTTP2 and SPDY. However, instead of being specialized for a higher-level protocol, muxado is designed in a protocol agnostic way with simplicity and speed in mind. More advanced features are left to higher-level libraries and protocols. muxado's API is designed to make it seamless to integrate into existing Go programs. muxado.Session implements the net.Listener interface and muxado.Stream implements net.Conn. muxado ships with two wrappers that add commonly used functionality. The first is a TypedStreamSession which allows a client application to open streams with a type identifier so that the remote peer can identify the protocol that will be communicated on that stream. The second wrapper is a simple Heartbeat which issues a callback to the application informing it of round-trip latency and heartbeat failure.

Package dcrjson provides infrastructure for working with Decred JSON-RPC APIs. When communicating via the JSON-RPC protocol, all requests and responses must be marshalled to and from the wire in the appropriate format. This package provides infrastructure and primitives to ease this process. This information is not necessary in order to use this package, but it does provide some intuition into what the marshalling and unmarshalling that is discussed below is doing under the hood. As defined by the JSON-RPC spec, there are effectively two forms of messages on the wire: Request Objects {"jsonrpc":"1.0","id":"SOMEID","method":"SOMEMETHOD","params":[SOMEPARAMS]} NOTE: Notifications are the same format except the id field is null. Response Objects {"result":SOMETHING,"error":null,"id":"SOMEID"} {"result":null,"error":{"code":SOMEINT,"message":SOMESTRING},"id":"SOMEID"} For requests, the params field can vary in what it contains depending on the method (a.k.a. command) being sent. Each parameter can be as simple as an int or a complex structure containing many nested fields. The id field is used to identify a request and will be included in the associated response. When working with streamed RPC transports, such as websockets, spontaneous notifications are also possible. As indicated, they are the same as a request object, except they have the id field set to null. Therefore, servers will ignore requests with the id field set to null, while clients can choose to consume or ignore them. Unfortunately, the original Bitcoin JSON-RPC API (and hence anything compatible with it) doesn't always follow the spec and will sometimes return an error string in the result field with a null error for certain commands. However, for the most part, the error field will be set as described on failure. To simplify the marshalling of the requests and responses, the MarshalCmd and MarshalResponse functions are provided. They return the raw bytes ready to be sent across the wire. Unmarshalling a received Request object is a two step process: This approach is used since it provides the caller with access to the additional fields in the request that are not part of the command such as the ID. Unmarshalling a received Response object is also a two step process: As above, this approach is used since it provides the caller with access to the fields in the response such as the ID and Error. This package provides the NewCmd function which takes a method (command) name and variable arguments. The function includes full checking to ensure the parameters are accurate according to provided method, however these checks are, obviously, run-time which means any mistakes won't be found until the code is actually executed. However, it is quite useful for user-supplied commands that are intentionally dynamic. External packages can and should implement types implementing Command for use with MarshalCmd/ParseParams. The command handling of this package is built around the concept of registered commands. This is true for the wide variety of commands already provided by the package, but it also means caller can easily provide custom commands with all of the same functionality as the built-in commands. Use the RegisterCmd function for this purpose. A list of all registered methods can be obtained with the RegisteredCmdMethods function. All registered commands are registered with flags that identify information such as whether the command applies to a chain server, wallet server, or is a notification along with the method name to use. These flags can be obtained with the MethodUsageFlags flags, and the method can be obtained with the CmdMethod function. To facilitate providing consistent help to users of the RPC server, this package exposes the GenerateHelp and function which uses reflection on registered commands or notifications to generate the final help text. In addition, the MethodUsageText function is provided to generate consistent one-line usage for registered commands and notifications using reflection. There are 2 distinct type of errors supported by this package: The first category of errors (type Error) typically indicates a programmer error and can be avoided by properly using the API. Errors of this type will be returned from the various functions available in this package. They identify issues such as unsupported field types, attempts to register malformed commands, and attempting to create a new command with an improper number of parameters. The specific reason for the error can be detected by type asserting it to a *dcrjson.Error and accessing the ErrorKind field. The second category of errors (type RPCError), on the other hand, are useful for returning errors to RPC clients. Consequently, they are used in the previously described Response type. This example demonstrates how to unmarshal a JSON-RPC response and then unmarshal the result field in the response to a concrete type.

Package shadow provides a PT 2.1 Go API wrapper around the connections used by Shadowsocks

Package replicant provides a PT 2.1 Go API implementation of the Replicant adversary-tunable transport

Package otel provides global access to the OpenTelemetry API. The subpackages of the otel package provide an implementation of the OpenTelemetry API. This package is currently in a pre-GA phase. Backwards incompatible changes may be introduced in subsequent minor version releases as we work to track the evolving OpenTelemetry specification and user feedback. The provided API is used to instrument code and measure data about that code's performance and operation. The measured data, by default, is not processed or transmitted anywhere. An implementation of the OpenTelemetry SDK, like the default SDK implementation (github.com/fwhappy/otel/sdk), and associated exporters are used to process and transport this data. To read more about tracing, see github.com/fwhappy/otel/trace. To read more about metrics, see github.com/fwhappy/otel/metric. To read more about propagation, see github.com/fwhappy/otel/propagation and github.com/fwhappy/otel/baggage.

Package p2phttp allows to serve HTTP endpoints and make HTTP requests through P2P (https://gitlab.dms3.io/p2p/p2p) using Go's standard "http" and "net" stacks. Instead of the regular "host:port" addressing, `p2phttp` uses a Peer ID and lets P2P take care of the routing, thus taking advantage of features like multi-routes, NAT transversal and stream multiplexing over a single connection. When already running a P2P facility, this package allows to expose existing HTTP-based services (like REST APIs) through P2P and to use those services with minimal changes to the code-base. For example, a simple http.Server on P2P works as: As shown above, a Server only needs a "gitlab.dms3.io/p2p/go-p2p-gostream" listener. This listener will use a p2p host to watch for stream tagged with our Protocol. On the other side, a client just needs to be initialized with a custom P2P host-based transport to perform requests to such server: In the example above, the client registers a "p2p" protocol for which the custom transport is used. It can still perform regular "http" requests. The protocol name used is arbitraty and non standard. Note that P2P hosts cannot dial to themselves, so there is no possibility of using the same host as server and as client.

Package sexprs implements Ron Rivest's canonical S-expressions (c.f. http://people.csail.mit.edu/rivest/Sexp.txt or rivest-draft.txt in this package) in Go. I'm indebted to Inferno's sexprs(2), whose API I first accidentally, and then deliberately, mimicked. I've copied much of its style, only making it more Go-like. Canonical S-expressions are a compact, easy-to-parse, ordered, hashable data representation ideal for cryptographic operations. They are simpler and more compact than either JSON or XML. An S-expression is composed of lists and atoms. An atom is a string of bytes, with an optional display hint, also a byte string. A list can contain zero or more atoms or lists. There are two representations of an S-expression: the canonical representation is a byte-oriented, packed representation, while the advanced representation is string-oriented and more traditional in appearance. The S-expression ("foo" "bar" ["bin"]"baz quux") is canonically: Among the valid advanced representations are: and: There is also a transport encoding (intended for use in 7-bit transport modes), delimited with {}:

Package protocol provides a object representation of a socket.io packet. This package currently supports socket.io version 1 to socket.io version 5. It provides classes and API to read and write socket.io wire format, as represented by: or as a real example: this is with the API: This object is expected to be written and read directly to the connection. It's a streaming but transport agnostic.

Package elasticsearch provides a Go client for Elasticsearch. Create the client with the NewDefaultClient function: The ELASTICSEARCH_URL environment variable is used instead of the default URL, when set. Use a comma to separate multiple URLs. To configure the client, pass a Config object to the NewClient function: When using the Elastic Service (https://elastic.co/cloud), you can use CloudID instead of Addresses. When either Addresses or CloudID is set, the ELASTICSEARCH_URL environment variable is ignored. See the elasticsearch_integration_test.go file and the _examples folder for more information. Call the Elasticsearch APIs by invoking the corresponding methods on the client: See the github.com/elastic/go-elasticsearch/esapi package for more information about using the API. See the github.com/elastic/elastic-transport-go package for more information about configuring the transport.

Package lockbox simplified asymmetric encryption with NaCl. Lockbox uses NaCl's box API for public-key cryptography to provide a simplified API for asymmetric encryption. It is designed with the following goals: * Provide a simple convention for managing encryption & decryption keys. An encryption key is a PEM encoded NaCl box public key with title "LOCKBOX PUBLIC ENCRYPTION KEY", stored with the file extension ".ekey". A decryption key is a PEM encoded NaCl box private key with title "LOCKBOX SECRET DECRYPTION KEY", stored with the file extension ".dkey". * Provide a simplified API for setup & encryption/decryption. The Encryptor & Decryptor types are constructed with their corresponding key. The types have a single Encrypt/Decrypt method that take a cleartext/ciphertext byte slice parameter and returns a ciphertext/cleartext byte slice. * Design the Encryptor so that it cannot decrypt the output of Encrypt once the function has returned. Isolating the role of decryption from encryption should be straightforward and easy. Install lockbox via go get: Generate a new keypair: Encrypt a message: Decrypt the message: Encrypt & print a message: Decrypt & print the message: Lockbox does not prevent a hostile party with access to the encryption key from replacing a message with a forgery. In this case, the decryptor is unable to detect if a message is a forgery. Lockbox data should only be transported over secure channels.

Package opensearch provides a Go client for OpenSearch. Create the client with the NewDefaultClient function: The OPENSEARCH_URL/ELASTICSEARCH_URL environment variable is used instead of the default URL, when set. Use a comma to separate multiple URLs. It is an error to set both environment variable. To configure the client, pass a Config object to the NewClient function: See the opensearch_integration_test.go file for more information. Call the OpenSearch APIs by invoking the corresponding methods on the client: See the github.com/opensearch-project/opensearch-go/opensearchapi package for more information about using the API. See the github.com/opensearch-project/opensearch-go/opensearchtransport package for more information about configuring the transport.

Package otel provides global access to the OpenTelemetry API. The subpackages of the otel package provide an implementation of the OpenTelemetry API. The provided API is used to instrument code and measure data about that code's performance and operation. The measured data, by default, is not processed or transmitted anywhere. An implementation of the OpenTelemetry SDK, like the default SDK implementation (github.com/grafana/opentelemetry-go/sdk), and associated exporters are used to process and transport this data. To read the getting started guide, see https://opentelemetry.io/docs/languages/go/getting-started/. To read more about tracing, see github.com/grafana/opentelemetry-go/trace. To read more about metrics, see github.com/grafana/opentelemetry-go/metric. To read more about propagation, see github.com/grafana/opentelemetry-go/propagation and github.com/grafana/opentelemetry-go/baggage.

Package elasticsearch provides a Go client for Elasticsearch. Create the client with the NewDefaultClient function: The ELASTICSEARCH_URL environment variable is used instead of the default URL, when set. Use a comma to separate multiple URLs. To configure the client, pass a Config object to the NewClient function: When using the Elastic Service (https://elastic.co/cloud), you can use CloudID instead of Addresses. When either Addresses or CloudID is set, the ELASTICSEARCH_URL environment variable is ignored. See the elasticsearch_integration_test.go file and the _examples folder for more information. Call the Elasticsearch APIs by invoking the corresponding methods on the client: See the github.com/elastic/go-elasticsearch/esapi package for more information about using the API. See the github.com/elastic/elastic-transport-go package for more information about configuring the transport.

The socketio package is a simple abstraction layer for different web browser- supported transport mechanisms. It is fully compatible with the Socket.IO client side JavaScript socket API library by LearnBoost Labs (http://socket.io/), but through custom codecs it might fit other client implementations too. It (together with the LearnBoost's client-side libraries) provides an easy way for developers to access the most popular browser transport mechanism today: multipart- and long-polling XMLHttpRequests, HTML5 WebSockets and forever-frames. The socketio package works hand-in-hand with the standard http package by plugging itself into a configurable ServeMux. It has an callback-style API for handling connection events. The callbacks are: - SocketIO.OnConnect - SocketIO.OnDisconnect - SocketIO.OnMessage Other utility-methods include: - SocketIO.ServeMux - SocketIO.Broadcast - SocketIO.BroadcastExcept - SocketIO.GetConn - Conn.Send Each new connection will be automatically assigned an unique session id and using those the clients can reconnect without losing messages: the server persists clients' pending messages (until some configurable point) if they can't be immediately delivered. All writes through Conn.Send by design asynchronous. Finally, the actual format on the wire is described by a separate Codec. The default codecs (SIOCodec and SIOStreamingCodec) are compatible with the LearnBoost's Socket.IO client. For example, here is a simple chat server:

Command goat provides an implementation of a BitTorrent tracker, written in Go. goat can be built using Go 1.1+. It can be downloaded, built, and installed, simply by running: In addition, goat depends on a MySQL server for data storage. After creating a database and user for goat, its database schema may be imported from the SQL files located in 'res/'. goat will not run unless MySQL is installed, and a database and user are properly configured for its use. Optionally, goat can be built to use ql (https://github.com/cznic/ql) as its storage backend. This is done by supplying the 'ql' tag in the go get command: A blank ql database file is located under 'res/ql/goat.db', and will be copied to '~/.config/goat/goat.db' on UNIX systems. goat is now able to use ql as its storage backend, for those who do not wish to use an external, MySQL backend. goat is capable of listening for torrent traffic in three modes: HTTP, HTTPS, and UDP. HTTP/HTTPS are the recommended methods, and are required in order for goat to serve its API, and to allow use of private tracker passkeys. HTTP is considered the standard mode of operation for goat. HTTP allows gathering a great number of metrics, use of passkeys, use of a client whitelist, and access to goat's RESTful API, when configured. For most trackers, this will be the only listener which is necessary in order for goat to function properly. The HTTPS listener provides a method to encrypt traffic to the tracker, but must be used with caution. Unless the SSL certificate in use is signed by a proper certificate authority, it will distress most clients, and they may outright refuse to announce to it. If you are in possession of a certificate signed by a certificate authority, this mode may be more ideal, as it provides added security for your clients. The UDP listener is the most unusual method of the three, and should only be used for public trackers. The BitTorrent UDP tracker protocol specifies a very specific packet format, meaning that additional information or parameters cannot be packed into a UDP datagram in a standard way. The UDP tracker may be the fastest and least bandwidth-intensive, but as stated, should only be used for public trackers. A new feature goat added to goat in order to allow better interoperability with many languages is a RESTful API, which is served using the HTTP or HTTPS listeners. This API enables easy retrieval of tracker statistics, while allowing goat to run as a completely independent process. It should be noted that the API is only enabled when configured, and when a HTTP or HTTPS listener is enabled. Without a transport mechanism, the API will be inaccessible. Currently, the API is read-only, and only allows use of the HTTP GET method. This may change in the future, but as of now, it doesn't make any sense to modify tracker parameters without doing a proper announce or scrape via BitTorrent client. The API will feature several modes of authentication, including HTTP Basic and HMAC-SHA1. For the time being, only HTTP Basic is implemented. This method makes use of a username/password pair using the user's username, and an API key as the password. This list contains all API calls currently recognized by goat. Each call must be authenticated using the aforementioned methods. Retrieve a list of all files tracked by goat. Some extended attributes are not added to reduce strain on database, and to provide a more general overview. Retrieve extended attributes about a specific file with matching ID. This provides counts for number of completions, seeders, leechers, and a list of fileUser relationships associated with a given file. Retrieve a variety of metrics about the current status of goat, including its PID, hostname, memory usage, number of HTTP/UDP hits, etc. goat is configured using a JSON file, which will be created under '~/.config/goat/config.json' on UNIX systems. Here is an example configuration, describing the settings available to the user.

Package yarpc provides the YARPC service framework. With hundreds to thousands of services communicating with RPC, transport protocols (like HTTP and TChannel), encoding protocols (like JSON or Thrift), and peer choosers are the concepts that vary year over year. Separating these concerns allows services to change transports and wire protocols without changing call sites or request handlers, build proxies and wire protocol bridges, or experiment with load balancing strategies. YARPC is a toolkit for services and proxies. YARPC breaks RPC into interchangeable encodings, transports, and peer choosers. YARPC for Go provides reference implementations for HTTP/1.1, TChannel and gRPC transports, and also raw, JSON, Thrift, and Protobuf encodings. YARPC for Go provides a round robin peer chooser and experimental implementations for debug pages and rate limiting. YARPC for Go plans to provide a load balancer that uses a least-pending-requests strategy. Peer choosers can implement any strategy, including load balancing or sharding, in turn bound to any peer list updater. Regardless of transport, every RPC has some common properties: caller name, service name, procedure name, encoding name, deadline or TTL, headers, baggage (multi-hop headers), and tracing. Each RPC can also have an optional shard key, routing key, or routing delegate for advanced routing. YARPC transports use a shared API for capturing RPC metadata, so middleware can apply to requests over any transport. Each YARPC transport protocol can implement inbound handlers and outbound callers. Each of these can support different RPC types, like unary (request and response) or oneway (request and receipt) RPC. A future release of YARPC will add support for other RPC types including variations on streaming and pubsub.

Package otel provides global access to the OpenTelemetry API. The subpackages of the otel package provide an implementation of the OpenTelemetry API. This package is currently in a pre-GA phase. Backwards incompatible changes may be introduced in subsequent minor version releases as we work to track the evolving OpenTelemetry specification and user feedback. The provided API is used to instrument code and measure data about that code's performance and operation. The measured data, by default, is not processed or transmitted anywhere. An implementation of the OpenTelemetry SDK, like the default SDK implementation (go.opentelemetry.io/otel/sdk), and associated exporters are used to process and transport this data. To read the getting started guide, see https://opentelemetry.io/docs/go/getting-started/. To read more about tracing, see go.opentelemetry.io/otel/trace. To read more about metrics, see go.opentelemetry.io/otel/metric. To read more about propagation, see go.opentelemetry.io/otel/propagation and go.opentelemetry.io/otel/baggage.

Provides an HTTP Transport that implements the `RoundTripper` interface and can be used as a built in replacement for the standard library's, providing: Internally, it uses a priority queue maintained in a single goroutine (per *client* instance), leveraging the Go 1.1+ `CancelRequest()` API.

Package optimizer provides a PT 2.0 Go API wrapper around the connections used

Package hyperdrive is an opinonated micro-framework for writing hypermedia APIs. It attempts to embrace the best of Hypermedia, especially the separation of client and server, encapsulated in the principle of HATEOAS (HTTP as the Engine of Application State). Hyperdrive APIs are resource-oriented, make heavy use of `http.Handler` middleware patterns, and takes advantage of HTTP verbs, headers, and other transport specific features, as much as possible. Other than that, it assumes nothing about how you store and retrieve your endpoint's hypermedia respresentations.

Package httpexpect helps with end-to-end HTTP and REST API testing. See example directory: There are two common ways to test API with httpexpect: The second approach works only if the server is a Go module and its handler can be imported in tests. Concrete behaviour is determined by Client implementation passed to Config struct. If you're using http.Client, set its Transport field (http.RoundTriper) to one of the following: Note that http handler can be usually obtained from http framework you're using. E.g., echo framework provides either http.Handler or fasthttp.RequestHandler. You can also provide your own implementation of RequestFactory (creates http.Request), or Client (gets http.Request and returns http.Response). If you're starting server from tests, it's very handy to use net/http/httptest. Whenever values are checked for equality in httpexpect, they are converted to "canonical form": This is equivalent to subsequently json.Marshal() and json.Unmarshal() the value and currently is implemented so. When some check fails, failure is reported. If non-fatal failures are used (see Reporter interface), execution is continued and instance that was checked is marked as failed. If specific instance is marked as failed, all subsequent checks are ignored for this instance and for any child instances retrieved after failure. Example:

Provides an HTTP Transport that implements the `RoundTripper` interface and can be used as a built in replacement for the standard library's, providing: This is a thin wrapper around `http.Transport` that sets dial timeouts and uses Go's internal timer scheduler to call the Go 1.1+ `CancelRequest()` API. Copyright 2015 mint.zhao.chiu@gmail.com Licensed under the Apache License, Version 2.0 (the "License"): you may not use this file except in compliance with the License. You may obtain a copy of the License at Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.

Package elasticsearch provides a Go client for Elasticsearch. Create the client with the NewDefaultClient function: The ELASTICSEARCH_URL environment variable is used instead of the default URL, when set. Use a comma to separate multiple URLs. To configure the client, pass a Config object to the NewClient function: When using the Elastic Service (https://elastic.co/cloud), you can use CloudID instead of Addresses. When either Addresses or CloudID is set, the ELASTICSEARCH_URL environment variable is ignored. See the elasticsearch_integration_test.go file and the _examples folder for more information. Call the Elasticsearch APIs by invoking the corresponding methods on the client: See the github.com/elastic/go-elasticsearch/esapi package for more information about using the API. See the github.com/elastic/go-elasticsearch/estransport package for more information about configuring the transport.

Package rollbar is a Golang Rollbar client that makes it easy to report errors to Rollbar with full stacktraces. Basic Usage This package is designed to be used via the functions exposed at the root of the `rollbar` package. These work by managing a single instance of the `Client` type that is configurable via the setter functions at the root of the package. If you wish for more fine grained control over the client or you wish to have multiple independent clients then you can create and manage your own instances of the `Client` type. We provide two implementations of the `Transport` interface, `AsyncTransport` and `SyncTransport`. These manage the communication with the network layer. The Async version uses a buffered channel to communicate with the Rollbar API in a separate go routine. The Sync version is fully synchronous. It is possible to create your own `Transport` and configure a Client to use your preferred implementation. Go does not provide a mechanism for handling all panics automatically, therefore we provide two functions `Wrap` and `WrapAndWait` to make working with panics easier. They both take a function and then report to Rollbar if that function panics. They use the recover mechanism to capture the panic, and therefore if you wish your process to have the normal behaviour on panic (i.e. to crash), you will need to re-panic the result of calling `Wrap`. For example, The above pattern of calling `Wrap(...)` and then `Wait(...)` can be combined via `WrapAndWait(...)`. When `WrapAndWait(...)` returns if there was a panic it has already been sent to the Rollbar API. The error is still returned by this function if there is one. Due to the nature of the `error` type in Go, it can be difficult to attribute errors to their original origin without doing some extra work. To account for this, we define the interface `CauseStacker`: One can implement this interface for custom Error types to be able to build up a chain of stack traces. In order to get stack the correct stacks, callers must call BuildStack on their own at the time that the cause is wrapped. This is the least intrusive mechanism for gathering this information due to the decisions made by the Go runtime to not track this information.

The API package provides the basic support for using HTTP to talk to the Mandrill and Mailchimp API's. Each Struct contains a Key, Transport and endpoint property

Package httpexpect helps with end-to-end HTTP and REST API testing. See example directory: There are two common ways to test API with httpexpect: The second approach works only if the server is a Go module and its handler can be imported in tests. Concrete behaviour is determined by Client implementation passed to Config struct. If you're using http.Client, set its Transport field (http.RoundTriper) to one of the following: Note that http handler can be usually obtained from http framework you're using. E.g., echo framework provides either http.Handler or fasthttp.RequestHandler. You can also provide your own implementation of RequestFactory (creates http.Request), or Client (gets http.Request and returns http.Response). If you're starting server from tests, it's very handy to use net/http/httptest. Whenever values are checked for equality in httpexpect, they are converted to "canonical form": This is equivalent to subsequently json.Marshal() and json.Unmarshal() the value and currently is implemented so. When some check fails, failure is reported. If non-fatal failures are used (see Reporter interface), execution is continued and instance that was checked is marked as failed. If specific instance is marked as failed, all subsequent checks are ignored for this instance and for any child instances retrieved after failure. Example:

Package pulseaudio is a pure-Go (no libpulse) implementation of the PulseAudio native protocol. Rather than exposing the PulseAudio protocol directly this library attempts to hide the PulseAudio complexity behind a Go interface. Some of the things which are deliberately not exposed in the API are: → backwards compatibility for old PulseAudio servers → transport mechanism used for the connection (Unix sockets / memfd / shm) → encoding used in the pulseaudio-native protocol Querying and setting the volume. Listing audio outputs. Changing the default audio output. Notifications on config updates.

Package elasticsearch provides a Go client for Elasticsearch. Create the client with the NewDefaultClient function: The ELASTICSEARCH_URL environment variable is used instead of the default URL, when set. Use a comma to separate multiple URLs. To configure the client, pass a Config object to the NewClient function: When using the Elastic Service (https://elastic.co/cloud), you can use CloudID instead of Addresses. When either Addresses or CloudID is set, the ELASTICSEARCH_URL environment variable is ignored. See the elasticsearch_integration_test.go file and the _examples folder for more information. Call the Elasticsearch APIs by invoking the corresponding methods on the client: See the github.com/elastic/go-elasticsearch/esapi package for more information about using the API. See the github.com/elastic/go-elasticsearch/estransport package for more information about configuring the transport.

Package elasticsearch provides a Go client for Elasticsearch. Create the client with the NewDefaultClient function: The ELASTICSEARCH_URL environment variable is used instead of the default URL, when set. Use a comma to separate multiple URLs. To configure the client, pass a Config object to the NewClient function: When using the Elastic Service (https://elastic.co/cloud), you can use CloudID instead of Addresses. When either Addresses or CloudID is set, the ELASTICSEARCH_URL environment variable is ignored. See the elasticsearch_integration_test.go file and the _examples folder for more information. Call the Elasticsearch APIs by invoking the corresponding methods on the client: See the github.com/elastic/go-elasticsearch/esapi package for more information about using the API. See the github.com/elastic/go-elasticsearch/estransport package for more information about configuring the transport.

Package httpexpect helps with end-to-end HTTP and REST API testing. See example directory: There are two common ways to test API with httpexpect: The second approach works only if the server is a Go module and its handler can be imported in tests. Concrete behaviour is determined by Client implementation passed to Config struct. If you're using http.Client, set its Transport field (http.RoundTriper) to one of the following: Note that http handler can be usually obtained from http framework you're using. E.g., echo framework provides either http.Handler or fasthttp.RequestHandler. You can also provide your own implementation of RequestFactory (creates http.Request), or Client (gets http.Request and returns http.Response). If you're starting server from tests, it's very handy to use net/http/httptest. Whenever values are checked for equality in httpexpect, they are converted to "canonical form": This is equivalent to subsequently json.Marshal() and json.Unmarshal() the value and currently is implemented so. When some check fails, failure is reported. If non-fatal failures are used (see Reporter interface), execution is continued and instance that was checked is marked as failed. If specific instance is marked as failed, all subsequent checks are ignored for this instance and for any child instances retrieved after failure. Example:

Package yarpc provides the YARPC service framework. With hundreds to thousands of services communicating with RPC, transport protocols (like HTTP and TChannel), encoding protocols (like JSON or Thrift), and peer choosers are the concepts that vary year over year. Separating these concerns allows services to change transports and wire protocols without changing call sites or request handlers, build proxies and wire protocol bridges, or experiment with load balancing strategies. YARPC is a toolkit for services and proxies. YARPC breaks RPC into interchangeable encodings, transports, and peer choosers. YARPC for Go provides reference implementations for HTTP/1.1, TChannel and gRPC transports, and also raw, JSON, Thrift, and Protobuf encodings. YARPC for Go provides a round robin peer chooser and experimental implementations for debug pages and rate limiting. YARPC for Go plans to provide a load balancer that uses a least-pending-requests strategy. Peer choosers can implement any strategy, including load balancing or sharding, in turn bound to any peer list updater. Regardless of transport, every RPC has some common properties: caller name, service name, procedure name, encoding name, deadline or TTL, headers, baggage (multi-hop headers), and tracing. Each RPC can also have an optional shard key, routing key, or routing delegate for advanced routing. YARPC transports use a shared API for capturing RPC metadata, so middleware can apply to requests over any transport. Each YARPC transport protocol can implement inbound handlers and outbound callers. Each of these can support different RPC types, like unary (request and response) or oneway (request and receipt) RPC. A future release of YARPC will add support for other RPC types including variations on streaming and pubsub.

Package httpexpect helps with end-to-end HTTP and REST API testing. See example directory: There are two common ways to test API with httpexpect: The second approach works only if the server is a Go module and its handler can be imported in tests. Concrete behaviour is determined by Client implementation passed to Config struct. If you're using http.Client, set its Transport field (http.RoundTriper) to one of the following: Note that http handler can be usually obtained from http framework you're using. E.g., echo framework provides either http.Handler or fasthttp.RequestHandler. You can also provide your own implementation of RequestFactory (creates http.Request), or Client (gets http.Request and returns http.Response). If you're starting server from tests, it's very handy to use net/http/httptest. Whenever values are checked for equality in httpexpect, they are converted to "canonical form": This is equivalent to subsequently json.Marshal() and json.Unmarshal() the value and currently is implemented so. When some check fails, failure is reported. If non-fatal failures are used (see Reporter interface), execution is continued and instance that was checked is marked as failed. If specific instance is marked as failed, all subsequent checks are ignored for this instance and for any child instances retrieved after failure. Example:

Package httpexpect helps with end-to-end HTTP and REST API testing. See example directory: There are two common ways to test API with httpexpect: The second approach works only if the server is a Go module and its handler can be imported in tests. Concrete behaviour is determined by Client implementation passed to Config struct. If you're using http.Client, set its Transport field (http.RoundTriper) to one of the following: Note that http handler can be usually obtained from http framework you're using. E.g., echo framework provides either http.Handler or fasthttp.RequestHandler. You can also provide your own implementation of RequestFactory (creates http.Request), or Client (gets http.Request and returns http.Response). If you're starting server from tests, it's very handy to use net/http/httptest. Whenever values are checked for equality in httpexpect, they are converted to "canonical form": This is equivalent to subsequently json.Marshal() and json.Unmarshal() the value and currently is implemented so. When some check fails, failure is reported. If non-fatal failures are used (see Reporter interface), execution is continued and instance that was checked is marked as failed. If specific instance is marked as failed, all subsequent checks are ignored for this instance and for any child instances retrieved after failure. Example:

Package rpc is a fork of the stdlib net/rpc which is frozen. It adds support for context.Context on the client and server, including propogating cancellation. See the README at https://github.com/keegancsmith/rpc for motivation why this exists. The API is exactly the same, except Client.Call takes a context.Context, and Server methods are expected to take a context.Context as the first argument. The following is the original rpc godoc updated to include context.Context. Additionally the wire protocol is unchanged, so is backwards compatible with net/rpc clients. Package rpc provides access to the exported methods of an object across a network or other I/O connection. A server registers an object, making it visible as a service with the name of the type of the object. After registration, exported methods of the object will be accessible remotely. A server may register multiple objects (services) of different types but it is an error to register multiple objects of the same type. Only methods that satisfy these criteria will be made available for remote access; other methods will be ignored: In effect, the method must look schematically like where T1 and T2 can be marshaled by encoding/gob. These requirements apply even if a different codec is used. (In the future, these requirements may soften for custom codecs.) The method's second argument represents the arguments provided by the caller; the third argument represents the result parameters to be returned to the caller. The method's return value, if non-nil, is passed back as a string that the client sees as if created by errors.New. If an error is returned, the reply parameter will not be sent back to the client. The server may handle requests on a single connection by calling ServeConn. More typically it will create a network listener and call Accept or, for an HTTP listener, HandleHTTP and http.Serve. A client wishing to use the service establishes a connection and then invokes NewClient on the connection. The convenience function Dial (DialHTTP) performs both steps for a raw network connection (an HTTP connection). The resulting Client object has two methods, Call and Go, that specify the service and method to call, a pointer containing the arguments, and a pointer to receive the result parameters. The Call method waits for the remote call to complete while the Go method launches the call asynchronously and signals completion using the Call structure's Done channel. Unless an explicit codec is set up, package encoding/gob is used to transport the data. Here is a simple example. A server wishes to export an object of type Arith: The server calls (for HTTP service): At this point, clients can see a service "Arith" with methods "Arith.Multiply" and "Arith.Divide". To invoke one, a client first dials the server: Then it can make a remote call: or A server implementation will often provide a simple, type-safe wrapper for the client. The net/rpc package is frozen and is not accepting new features.

The socketio package is a simple abstraction layer for different web browser- supported transport mechanisms. It is fully compatible with the Socket.IO client side JavaScript socket API library by LearnBoost Labs (http://socket.io/), but through custom codecs it might fit other client implementations too. It (together with the LearnBoost's client-side libraries) provides an easy way for developers to access the most popular browser transport mechanism today: multipart- and long-polling XMLHttpRequests, HTML5 WebSockets and forever-frames. The socketio package works hand-in-hand with the standard http package by plugging itself into a configurable ServeMux. It has an callback-style API for handling connection events. The callbacks are: - SocketIO.OnConnect - SocketIO.OnDisconnect - SocketIO.OnMessage Other utility-methods include: - SocketIO.ServeMux - SocketIO.Broadcast - SocketIO.BroadcastExcept - SocketIO.GetConn - Conn.Send Each new connection will be automatically assigned an unique session id and using those the clients can reconnect without losing messages: the server persists clients' pending messages (until some configurable point) if they can't be immediately delivered. All writes through Conn.Send by design asynchronous. Finally, the actual format on the wire is described by a separate Codec. The default codecs (SIOCodec and SIOStreamingCodec) are compatible with the LearnBoost's Socket.IO client. For example, here is a simple chat server:

Package mcxjson provides infrastructure for working with MultiCash JSON-RPC APIs. When communicating via the JSON-RPC protocol, all requests and responses must be marshalled to and from the wire in the appropriate format. This package provides infrastructure and primitives to ease this process. This information is not necessary in order to use this package, but it does provide some intuition into what the marshalling and unmarshalling that is discussed below is doing under the hood. As defined by the JSON-RPC spec, there are effectively two forms of messages on the wire: Request Objects {"jsonrpc":"1.0","id":"SOMEID","method":"SOMEMETHOD","params":[SOMEPARAMS]} NOTE: Notifications are the same format except the id field is null. Response Objects {"result":SOMETHING,"error":null,"id":"SOMEID"} {"result":null,"error":{"code":SOMEINT,"message":SOMESTRING},"id":"SOMEID"} For requests, the params field can vary in what it contains depending on the method (a.k.a. command) being sent. Each parameter can be as simple as an int or a complex structure containing many nested fields. The id field is used to identify a request and will be included in the associated response. When working with streamed RPC transports, such as websockets, spontaneous notifications are also possible. As indicated, they are the same as a request object, except they have the id field set to null. Therefore, servers will ignore requests with the id field set to null, while clients can choose to consume or ignore them. Unfortunately, the original Bitcoin JSON-RPC API (and hence anything compatible with it) doesn't always follow the spec and will sometimes return an error string in the result field with a null error for certain commands. However, for the most part, the error field will be set as described on failure. To simplify the marshalling of the requests and responses, the MarshalCmd and MarshalResponse functions are provided. They return the raw bytes ready to be sent across the wire. Unmarshalling a received Request object is a two step process: This approach is used since it provides the caller with access to the additional fields in the request that are not part of the command such as the ID. Unmarshalling a received Response object is also a two step process: As above, this approach is used since it provides the caller with access to the fields in the response such as the ID and Error. This package provides the NewCmd function which takes a method (command) name and variable arguments. The function includes full checking to ensure the parameters are accurate according to provided method, however these checks are, obviously, run-time which means any mistakes won't be found until the code is actually executed. However, it is quite useful for user-supplied commands that are intentionally dynamic. External packages can and should implement types implementing Command for use with MarshalCmd/ParseParams. The command handling of this package is built around the concept of registered commands. This is true for the wide variety of commands already provided by the package, but it also means caller can easily provide custom commands with all of the same functionality as the built-in commands. Use the RegisterCmd function for this purpose. A list of all registered methods can be obtained with the RegisteredCmdMethods function. All registered commands are registered with flags that identify information such as whether the command applies to a chain server, wallet server, or is a notification along with the method name to use. These flags can be obtained with the MethodUsageFlags flags, and the method can be obtained with the CmdMethod function. To facilitate providing consistent help to users of the RPC server, this package exposes the GenerateHelp and function which uses reflection on registered commands or notifications to generate the final help text. In addition, the MethodUsageText function is provided to generate consistent one-line usage for registered commands and notifications using reflection. There are 2 distinct type of errors supported by this package: The first category of errors (type Error) typically indicates a programmer error and can be avoided by properly using the API. Errors of this type will be returned from the various functions available in this package. They identify issues such as unsupported field types, attempts to register malformed commands, and attempting to create a new command with an improper number of parameters. The specific reason for the error can be detected by type asserting it to a *mcxjson.Error and accessing the ErrorKind field. The second category of errors (type RPCError), on the other hand, are useful for returning errors to RPC clients. Consequently, they are used in the previously described Response type. This example demonstrates how to unmarshal a JSON-RPC response and then unmarshal the result field in the response to a concrete type.

Package elasticsearch provides a Go client for Elasticsearch. Create the client with the NewDefaultClient function: The ELASTICSEARCH_URL environment variable is used instead of the default URL, when set. Use a comma to separate multiple URLs. To configure the client, pass a Config object to the NewClient function: When using the Elastic Service (https://elastic.co/cloud), you can use CloudID instead of Addresses. When either Addresses or CloudID is set, the ELASTICSEARCH_URL environment variable is ignored. See the elasticsearch_integration_test.go file and the _examples folder for more information. Call the Elasticsearch APIs by invoking the corresponding methods on the client: See the github.com/elastic/go-elasticsearch/esapi package for more information about using the API. See the github.com/elastic/go-elasticsearch/estransport package for more information about configuring the transport.

Package bronjson provides primitives for working with the brocoin JSON-RPC API. When communicating via the JSON-RPC protocol, all of the commands need to be marshalled to and from the the wire in the appropriate format. This package provides data structures and primitives to ease this process. In addition, it also provides some additional features such as custom command registration, command categorization, and reflection-based help generation. This information is not necessary in order to use this package, but it does provide some intuition into what the marshalling and unmarshalling that is discussed below is doing under the hood. As defined by the JSON-RPC spec, there are effectively two forms of messages on the wire: Request Objects {"jsonrpc":"1.0","id":"SOMEID","method":"SOMEMETHOD","params":[SOMEPARAMS]} NOTE: Notifications are the same format except the id field is null. Response Objects {"result":SOMETHING,"error":null,"id":"SOMEID"} {"result":null,"error":{"code":SOMEINT,"message":SOMESTRING},"id":"SOMEID"} For requests, the params field can vary in what it contains depending on the method (a.k.a. command) being sent. Each parameter can be as simple as an int or a complex structure containing many nested fields. The id field is used to identify a request and will be included in the associated response. When working with asynchronous transports, such as websockets, spontaneous notifications are also possible. As indicated, they are the same as a request object, except they have the id field set to null. Therefore, servers will ignore requests with the id field set to null, while clients can choose to consume or ignore them. Unfortunately, the original Brocoin JSON-RPC API (and hence anything compatible with it) doesn't always follow the spec and will sometimes return an error string in the result field with a null error for certain commands. However, for the most part, the error field will be set as described on failure. Based upon the discussion above, it should be easy to see how the types of this package map into the required parts of the protocol To simplify the marshalling of the requests and responses, the MarshalCmd and MarshalResponse functions are provided. They return the raw bytes ready to be sent across the wire. Unmarshalling a received Request object is a two step process: This approach is used since it provides the caller with access to the additional fields in the request that are not part of the command such as the ID. Unmarshalling a received Response object is also a two step process: As above, this approach is used since it provides the caller with access to the fields in the response such as the ID and Error. This package provides two approaches for creating a new command. This first, and preferred, method is to use one of the New<Foo>Cmd functions. This allows static compile-time checking to help ensure the parameters stay in sync with the struct definitions. The second approach is the NewCmd function which takes a method (command) name and variable arguments. The function includes full checking to ensure the parameters are accurate according to provided method, however these checks are, obviously, run-time which means any mistakes won't be found until the code is actually executed. However, it is quite useful for user-supplied commands that are intentionally dynamic. The command handling of this package is built around the concept of registered commands. This is true for the wide variety of commands already provided by the package, but it also means caller can easily provide custom commands with all of the same functionality as the built-in commands. Use the RegisterCmd function for this purpose. A list of all registered methods can be obtained with the RegisteredCmdMethods function. All registered commands are registered with flags that identify information such as whether the command applies to a chain server, wallet server, or is a notification along with the method name to use. These flags can be obtained with the MethodUsageFlags flags, and the method can be obtained with the CmdMethod function. To facilitate providing consistent help to users of the RPC server, this package exposes the GenerateHelp and function which uses reflection on registered commands or notifications, as well as the provided expected result types, to generate the final help text. In addition, the MethodUsageText function is provided to generate consistent one-line usage for registered commands and notifications using reflection. There are 2 distinct type of errors supported by this package: The first category of errors (type Error) typically indicates a programmer error and can be avoided by properly using the API. Errors of this type will be returned from the various functions available in this package. They identify issues such as unsupported field types, attempts to register malformed commands, and attempting to create a new command with an improper number of parameters. The specific reason for the error can be detected by type asserting it to a *bronjson.Error and accessing the ErrorCode field. The second category of errors (type RPCError), on the other hand, are useful for returning errors to RPC clients. Consequently, they are used in the previously described Response type. This example demonstrates how to unmarshal a JSON-RPC response and then unmarshal the result field in the response to a concrete type.