code: func (c ControlHandler) HandlePong(h ws.Header) error {
  	if h.Length == 0 {
  		return nil
  	}
  
  	buf := pbytes.GetLen(int(h.Length))
  	defer pbytes.Put(buf)
  
  	// Discard pong message according to the RFC6455:
  	// A Pong frame MAY be sent unsolicited. This serves as a
  	// unidirectional heartbeat. A response to an unsolicited Pong frame
  	// is not expected.
  	_, err := io.CopyBuffer(ioutil.Discard, c.Src, buf)
  
  	return err
  }
docs: // HandlePong handles pong frame by discarding it.