code: func (a *Audio) Send(b *Bot, to Recipient, opt *SendOptions) (*Message, error) {
  	params := map[string]string{
  		"chat_id":   to.Recipient(),
  		"caption":   a.Caption,
  		"performer": a.Performer,
  		"title":     a.Title,
  	}
  
  	if a.Duration != 0 {
  		params["duration"] = strconv.Itoa(a.Duration)
  	}
  
  	embedSendOptions(params, opt)
  
  	msg, err := b.sendObject(&a.File, "audio", params, nil)
  	if err != nil {
  		return nil, err
  	}
  
  	if msg.Audio != nil {
  		msg.Audio.File.stealRef(&a.File)
  		*a = *msg.Audio
  	}
  
  	if msg.Document != nil {
  		msg.Document.File.stealRef(&a.File)
  		a.File = msg.Document.File
  	}
  
  	return msg, nil
  }
docs: // Send delivers media through bot b to recipient.