code: func NewClientWithSender(sender Sender, prefix string) (Statter, error) {
  	if sender == nil {
  		return nil, fmt.Errorf("Client sender may not be nil")
  	}
  
  	return &Client{prefix: prefix, sender: sender}, nil
  }
docs: // NewClientWithSender returns a pointer to a new Client and an error.
  //
  // sender is an instance of a statsd.Sender interface and may not be nil
  //
  // prefix is the stastd client prefix. Can be "" if no prefix is desired.