Go tutorial.

1. Deal with JSON file

• parse

json.Unmarshal

• stringify(js)

json.Marshal

2. Deal with environment variables

    // load some ENV files first (".dev.env", prod.env)
	err := godotenv.Load()

	if err != nil {
		log.Fatal("Error, loading env fail")
	}
	// Load successfull then get Key
	key := os.Getenv("SUPER_KEY")
	log.Println("KEY", key)

3. Composition vs inheritace