aconfig's Introduction

aconfig

Simple, useful and opinionated config loader.

Rationale

There are more than 2000 repositories on Github regarding configuration in Go. I was looking for a simple configuration loader that will automate a lot of things for me. Idea was to load config from 4 common places: defaults (in the code), config files, environment variables, command-line flags. This library works with all of them.

Features

Simple API.
Automates a lot of things.
Opinionated.
Supports different sources:
- defaults in code
- files (JSON, YAML, TOML)
- environment variables
- command-line flags
Dependency-free (except file parsers).
Walk over configuration fields.

Install

Go version 1.14+

go get github.com/cristalhq/aconfig

Example

type MyConfig struct {
	Port int `default:"1111" usage:"just give a number"`
	Auth struct {
		User string `default:"def-user"`
		Pass string `default:"def-pass"`
	}
	Pass string `default:"" env:"SECRET" flag:"sec_ret"`
}

loader := aconfig.LoaderFor(&MyConfig{}).
	// feel free to skip some steps :)
	// SkipDefaults().
	// SkipFiles().
	// SkipEnvironment().
	// SkipFlags().
	WithFiles([]string{"file.json", "ouch.yaml"}).
	WithEnvPrefix("APP").
	WithFlagPrefix("app").
	Build()

flagSet := loader.Flags() // now use exactly this flags to define your own

var cfg MyConfig
if err := loader.Load(&cfg); err != nil {
	panic(err)
}

// configuration fields will be loaded from (in order):
//
// 1. defaults set in structure tags (see structure defenition)
// 2. loaded from files `file.json` if not `ouch.yaml` will be used
// 3. from corresponding environment variables with prefix `APP`
// 4. and command-line flags if they are