code: func (b *Bot) Respond(callback *Callback, responseOptional ...*CallbackResponse) error {
  	var response *CallbackResponse
  	if responseOptional == nil {
  		response = &CallbackResponse{}
  	} else {
  		response = responseOptional[0]
  	}
  
  	response.CallbackID = callback.ID
  	respJSON, err := b.Raw("answerCallbackQuery", response)
  	if err != nil {
  		return err
  	}
  
  	return extractOkResponse(respJSON)
  }
docs: // Respond sends a response for a given callback query. A callback can
  // only be responded to once, subsequent attempts to respond to the same callback
  // will result in an error.
  //
  // Example:
  //
  //		bot.Respond(c)
  //		bot.Respond(c, response)
  //