code: func (t *TokenRefresher) RefreshAuthToken() (string, error) {
  	tokens, err := t.uaaClient.RefreshAccessToken(t.cache.RefreshToken())
  	if err != nil {
  		return "", err
  	}
  
  	t.cache.SetAccessToken(tokens.AuthorizationToken())
  	t.cache.SetRefreshToken(tokens.RefreshToken)
  	return tokens.AuthorizationToken(), nil
  }
docs: // RefreshAuthToken refreshes the current Authorization Token and stores the
  // Access and Refresh token in it's cache. The returned Authorization Token
  // includes the type prefixed by a space.