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

Install by running:

go get -u github.com/Luzifer/rconfig/v2

Run tests by running in the checkout folder:

go test -v -race -cover ./...

A very simple usecase is to just configure a struct inside the vars section of your main.go and to parse the commandline flags from the main() function:

package main

import (
  "fmt"
  "github.com/Luzifer/rconfig/v2"
)

var (
  cfg = struct {
    Username string `default:"unknown" flag:"user" description:"Your name"`
    Details  struct {
      Age int `default:"25" flag:"age" env:"age" description:"Your age"`
    }
  }{}
)

func main() {
  rconfig.Parse(&cfg)

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

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

var cfg = struct {
  Username string `vardefault:"username" flag:"username" description:"Your username"`
}

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

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

You can see the full reference documentation of the rconfig package at pkg.go.dev