What is it?

Tiny (1 line) GO package to deal with complex configs provided through environment variables.

Why we need it?

In dockerized applications and by https://12factor.net/ recommendation we have to pass configuration for our GO program through environment variables.

It is easy if configuration consists of simple values (strings, numbers, boolean, etc), something like this:

{
      "login":"user",
      "password":"somepass",
      "mfa_enabled": true
}

In this case we could use several environment variables like APP_LOGIN="user" APP_PASSWORD="somepass".

But how would we work with complex configuration that, for example, consists of arrays of objects? For example:

{
      "nodes":[
            {
                  "url":"http://1.localhost/",
                  "priority":1,
                  "enabled":true
            },
            {
                  "url":"http://2.localhost/",
                  "priority":2,
                  "enabled":false
            }
      ]
}

This package is aimed to deal with such configs. Just put the config into single environment variable. It could be multiline, but work with single line is simplier from bash.

Running program bash example:

CONFIG='{"nodes":[{"url":"http:\/\/1.localhost\/","priority":1,"enabled":true},{"url":"http:\/\/2.localhost\/","priority":2,"enabled":false}]}' ./app

GO program code example:

import jsonEnvGo "github.com/antelman107/json-env-go"

type Config struct {
	Nodes []struct {
		URL      string `json:"url"`
		Priority int    `json:"priority"`
		Enabled  bool   `json:"enabled"`
	} `json:"nodes"`
}

func main() {
      var cfg Config
      if err := jsonEnvGo.DecodeConfigFromEnv("CONFIG", &cfg); err != nil {
            logger.Error(err)
            return
      }
      
      // cfg now filled, do something with it
      // ...
}

This package is very tiny, it can be used instead of viper (https://github.com/spf13/viper) when working especially with json configs coming from environment variables.