https://ibraheem.ca/posts/go-global-config-files

# Golang Global Configuration Files.md

A simple way to decode configuration files based on the current application environment into globally accessible variables

The code for Golang Global Configuration Files with Multiple Environments

config.go

// config/config.go

package config

import (
	"fmt"
	"log"
	"os"

	"github.com/joho/godotenv"
	"gopkg.in/yaml.v3"
)

// Config : application config stored as global variable
var Config *EnvironmentConfig

// EnvironmentConfig :
type EnvironmentConfig struct {
  Server ServerConfig `yaml:"server"`
}

// ServerConfig :
type ServerConfig struct {
  Host   string  `yaml:"host"`
  Port   integer `yaml:"port"`
  Static struct {
    BuildPath string `yaml:"buildpath"`
  } `yaml:"static"`
}

// assign global config to decoded config struct
func init() {
	Config = readConfig()
}

func readConfig() *EnvironmentConfig {
	file := fmt.Sprintf("config/environments/%s.yml", getEnv())
	f, err := os.Open(file)
	if err != nil {
		log.Fatal(err)
		os.Exit(2)
	}
	defer f.Close()

	var cfg EnvironmentConfig
	decoder := yaml.NewDecoder(f)
	err = decoder.Decode(&cfg)
	if err != nil {
		log.Fatal(err)
		os.Exit(2)
	}
	return &cfg
}

// getEnv : get configuration environment variable
func getEnv() string {
	err := godotenv.Load()
	if err != nil {
		log.Fatal("Error loading .env file")
	}
	return os.Getenv("APP_ENV")
}

env

# development, production, or testing environment
APP_ENV=development

environments.yml

# config/environments/{development, production, testing}.yml

server:
  host: "localhost"
  port: 5000
  static:
    buildpath: "client/build"

main.go

package main

// lazily import config package for init function

import (
  _ "github.com/yourapp/config"
)

...

router.go

// an example of accessing the global app config

package main

import (
  "fmt"
  "log"
  "net/http"
  "github.com/yourapp/config"
)

// access global config variable
var routerConfig config.ServerConfig = config.Config.Server

// ListenAndServe :
func ListenAndServe() {
  log.Fatal(
    http.ListenAndServe(
      // use http host and port config variables
      fmt.Sprintf("%s:%s", routerConfig.Host, routerConfig.Port),
      initRoutes()))
}