rconfig

Description

Package rconfig implements a CLI configuration reader with struct-embedded defaults, environment variables and posix compatible flag parsing using the pflag library.

Installation

Install by running:

go get -u github.com/Luzifer/rconfig

Run tests by running:

go test -v -race -cover github.com/Luzifer/rconfig

Usage

As a first step define a struct holding your configuration:

type config struct {
  Username string `default:"unknown" flag:"user" description:"Your name"`
  Details  struct {
    Age int `default:"25" flag:"age" env:"age" description:"Your age"`
  }
}

Next create an instance of that struct and let rconfig fill that config:

var cfg config
func init() {
  cfg = config{}
  rconfig.Parse(&cfg)
}

You're ready to access your configuration:

func main() {
  fmt.Printf("Hello %s, happy birthday for your %dth birthday.",
		cfg.Username,
		cfg.Details.Age)
}

Provide variable defaults by using a file

Given you have a file ~/.myapp.yml containing some secrets or usernames (for the example below username is assumed to be "luzifer") as a default configuration for your application you can use this source code to load the defaults from that file using the vardefault tag in your configuration struct.

The order of the directives (lower number = higher precedence):

1. Flags provided in command line
2. Environment variables
3. Variable defaults (vardefault tag in the struct)
4. default tag in the struct

type config struct {
  Username string `vardefault:"username" flag:"username" description:"Your username"`
}

var cfg = config{}

func init() {
  rconfig.SetVariableDefaults(VarDefaultsFromYAMLFile("~/.myapp.yml"))
  rconfig.Parse(&cfg)
}

func main() {
  fmt.Printf("Username = %s", cfg.Username)
  // Output: Username = luzifer
}

More info

You can see the full reference documentation of the rconfig package at godoc.org, or through go's standard documentation system by running godoc -http=:6060 and browsing to http://localhost:6060/pkg/github.com/Luzifer/rconfig after installation.