code: func (bot *BotAPI) sendExisting(method string, config Fileable) (Message, error) {
  	v, err := config.values()
  
  	if err != nil {
  		return Message{}, err
  	}
  
  	message, err := bot.makeMessageRequest(method, v)
  	if err != nil {
  		return Message{}, err
  	}
  
  	return message, nil
  }
docs: // sendExisting will send a Message with an existing file to Telegram.