github.com/elastic/go-ucfg

ucfg - Universal Configuration

ucfg is a Golang library to handle hjson, json, and yaml configuration files in your Golang project. It was developed for the libbeat framework and used by all beats.

API Documentation

The full API Documentation can be found here.

Examples

A few examples on how ucfg can be used. All examples below assume, that the following packages are imported:

import (
	"github.com/elastic/go-ucfg"
	"github.com/elastic/go-ucfg/yaml"
)

Dot notations

ufcg allows you to load yaml configuration files using dots instead of indentation. For example instead of having:

config:
  user: name

with ucfg you can write:

config.user: name

This makes configurations easier and simpler.

To load such a config file in Golang, use the following command:

config, err := yaml.NewConfigWithFile(path, ucfg.PathSep("."))

Validation and Defaults

ucfg allows to automatically validate fields and set defaults for fields in case they are not defined.

// Defines struct to read config from
type ExampleConfig struct {
    Counter  int 	`config:"counter" validate:"min=0, max=9"`
}

// Defines default config option
var (
    defaultConfig = ExampleConfig{
		    Counter: 4,
    }
)

func main() {
    appConfig := defaultConfig // copy default config so it's not overwritten
    config, err := yaml.NewConfigWithFile(path, ucfg.PathSep("."))
    if err != nil {
        fmt.Println(err)
        os.Exit(1)
    }
    err = config.Unpack(&appConfig)
    if err != nil {
        fmt.Println(err)
        os.Exit(1)
    }
}

The above uses Counter as the config variable. ucfg assures that the value is between 0 and 9 and will return an error if this is not the case. In addition, if the value is not set, it will default to 4.

Requirements

ucfg has the following requirements:

• Golang 1.10+