Simple, useful and opinionated config loader.
There are many solutions regarding configuration loading in Go. I was looking for a simple loader that is as easy to use and understand as possible. The goal was to load config from 4 places: defaults (in the code), files, environment variables, command-line flags. This library works with all of these sources.
- Simple API.
- Clean and tested code.
- Automatic fields mapping.
- Supports different sources:
- defaults in the code
- files (JSON, YAML, TOML, DotENV, HCL)
- environment variables
- command-line flags
- Dependency-free (file parsers are optional).
- Ability to walk over configuration fields.
Go version 1.14+
go get github.com/cristalhq/aconfig
type MyConfig struct {
Port int `default:"1111" usage:"just give a number"`
Auth struct {
User string `required:"true"`
Pass string `required:"true"`
}
Pass string `default:"" env:"SECRET" flag:"sec_ret"`
}
var cfg MyConfig
loader := aconfig.LoaderFor(&cfg, aconfig.Config{
// feel free to skip some steps :)
// SkipDefaults: true,
// SkipFiles: true,
// SkipEnv: true,
// SkipFlags: true,
EnvPrefix: "APP",
FlagPrefix: "app",
Files: []string{"/var/opt/myapp/config.json", "ouch.yaml"},
FileDecoders: map[string]aconfig.FileDecoder{
// from `aconfigyaml` submodule
// see submodules in repo for more formats
".yaml": aconfigyaml.New(),
},
})
// IMPORTANT: define your own flags with `flagSet`
flagSet := loader.Flags()
if err := loader.Load(); err != nil {
panic(err)
}
// configuration fields will be loaded from (in order):
//
// 1. defaults set in structure tags (see MyConfig defenition)
// 2. loaded from files `file.json` if not `ouch.yaml` will be used
// 3. from corresponding environment variables with the prefix `APP_`
// 4. command-line flags with the prefix `app.` if they areAlso see examples: examples_test.go.
Integration with spf13/cobra playground.
See these docs.