// After such a timeout, writes by h to its [ResponseWriter] will return
// [ErrHandlerTimeout].
//
// TimeoutHandler supports the [Pusher] interface but does not support
// the [Hijacker] or [Flusher] interfaces.
func TimeoutHandler(h Handler, dt time.Duration, msg string) Handler {
	return &timeoutHandler{
		handler: h,
		body:    msg,
		dt:      dt,
	}
}

// Both issues involved panics in the implementation of TimeoutHandler.
func TestTimeoutHandlerRaceHeader(t *testing.T) { run(t, testTimeoutHandlerRaceHeader) }
func testTimeoutHandlerRaceHeader(t *testing.T, mode testMode) {
	delay204 := HandlerFunc(func(w ResponseWriter, r *Request) {
		w.WriteHeader(204)
	})

	ts := newClientServerTest(t, mode, TimeoutHandler(delay204, time.Nanosecond, "")).ts

	var wg sync.WaitGroup