code: func (h *Client) ScreenName(screenName string) *Client {
  	h.screenName = screenName
  	h.screenNameSet = true
  	return h
  }
docs: // If not specified, this will default to the unique URL of
  // the page by either using the &dl parameter as-is or assembling
  // it from &dh and &dp. App tracking makes use of this for
  // the 'Screen Name' of the screenview hit.