code: func Getenv(key string, v ...string) string {
  	defaultValue := ""
  	if len(v) > 0 {
  		defaultValue = v[0]
  	}
  
  	value := os.Getenv(key)
  	if value == "" {
  		return defaultValue
  	}
  	return value
  }
docs: // Getenv retrieves the value of the environment variable named by the key.
  // It returns the value, which will the default value if the variable is not present.
  // If no default value was given - returns "".