code: func getExpandedAddress(user, instanceURL string) (string, error) {
  
  	if user == "" || instanceURL == "" {
  		return "", errors.New("some required account data is missing")
  	}
  
  	parsedURL, err := url.Parse(instanceURL)
  	if err != nil {
  		return "", err
  	}
  
  	return fmt.Sprintf("@%s@%s", user, parsedURL.Host), nil
  }
docs: // getExpandedAddress returns the address for the account in the @user@example.com form