code: func (a *PromptingAuthLoader) Prompt() (*clientauth.Info, error) {
  	var err error
  	auth := &clientauth.Info{}
  	auth.User, err = promptForString("Username", a.reader, true)
  	if err != nil {
  		return nil, err
  	}
  	auth.Password, err = promptForString("Password", nil, false)
  	if err != nil {
  		return nil, err
  	}
  	return auth, nil
  }
docs: // Prompt pulls the user and password from a reader