code: func (rm *responseModifier) Hijack() (net.Conn, *bufio.ReadWriter, error) {
  
  	rm.hijacked = true
  	rm.FlushAll()
  
  	hijacker, ok := rm.rw.(http.Hijacker)
  	if !ok {
  		return nil, nil, fmt.Errorf("Internal response writer doesn't support the Hijacker interface")
  	}
  	return hijacker.Hijack()
  }
docs: // Hijack returns the internal connection of the wrapped http.ResponseWriter