code: func (c *Bot) PMURL(param string) string {
  	if param == "" {
  		return fmt.Sprintf("https://telegram.me/%v", c.Username)
  	}
  
  	return fmt.Sprintf("https://telegram.me/%v?start=%v", c.Username, param)
  }
docs: // PMURL return URL to private messaging with the bot like https://telegram.me/trello_bot?start=param