Go Yaml Config

Configure your Golang project using a Yaml file who accepts env variables on his strings just like a docker-compose file.

Summary

Features
Example
Limitations

Features

Full yaml parsing: go-yaml-config uses go-yaml for parsing the config files
Env Variables support: all the env variables patterns found on the strings of the config file will be replaced with the respective env or default value, when a default is not provided and the env is not setted, the value will be an empty string.
Type Safety: the config struct type has to be defined on the code, and passed to the config initialization as a generic type argument. In the same way, it is retrieved on the same type as a generic argument. If the type is mismatched, you can handle the error or simply let the application panics with The Must Function.
Singleton Pattern: The initialization guarantees that the config is only initialized once. And all the get operations are always in a constant time complexity.

Example

First, create a config file for your application on any accessible path with any name, in this case will be on the app root: ./appSettings.yml, with the follow content:

dbSettings:
  host: "localhost"
  port: 5432
  name: "someDB"
  user: "someUser"
  pass: "${PASS:-somePass}"

Then create the corresponding struct in your Go app and initialize the config:

package main

import (
    	"fmt"
    	conf "github.com/Mth-Ryan/go-yaml-cfg"
)

// Struct Fields must be public
type AppSettings struct {
    	DBSettings struct {
            	Host string `yaml:"host"`
            	Port int    `yaml:"port"`
            	Name string `yaml:"name"`
            	User string `yaml:"user"`
            	Pass string `yaml:"pass"`
    	} `yaml:"dbSettings"`
}

func main() {
    	var config AppSettings
    	var err error

    	if err = conf.InitializeConfigSingleton[AppSettings]("./appSettings.yml"); err != nil {
            	panic(err)
    	}

    	config, err = conf.GetConfigFromSingleton[AppSettings]()
    	if err != nil {
            	panic(err)
    	}
    	fmt.Printf("%+v \n", config)
}

If you build and run this project you will get:

go build -o test
./test
{DBSettings:{Host:localhost Port:5432 Name:someDB User:someUser Pass:somePass}}

Now Overriding the default password with a env variable:

PASS="otherPass" ./test
{DBSettings:{Host:localhost Port:5432 Name:someDB User:someUser Pass:otherPass}}

Limitations

The env replacement don't work with maps whatsoever, so you are limited to structs, slices and arrays for that.
All the fields must be public, this is a limitation of go's reflection lib, there is no way to change this.
The lib requires go >= 1.18