code: func (c ControlHandler) Handle(h ws.Header) error {
  	switch h.OpCode {
  	case ws.OpPing:
  		return c.HandlePing(h)
  	case ws.OpPong:
  		return c.HandlePong(h)
  	case ws.OpClose:
  		return c.HandleClose(h)
  	}
  	return ErrNotControlFrame
  }
docs: // Handle handles control framse regarding to the c.State and writes responses
  // to the c.Dst when needed.
  //
  // It returns ErrNotControlFrame when given header is not of ws.OpClose,
  // ws.OpPing or ws.OpPong operation code.