// New code should use [Request.Context] instead.
type CloseNotifier interface {
	// CloseNotify returns a channel that receives at most a
	// single value (true) when the client connection has gone
	// away.
	//
	// CloseNotify may wait to notify until Request.Body has been
	// fully read.
	//
	// After the Handler has returned, there is no guarantee

	script := make(chan string, 2)
	script <- "closenotify"
	script <- "hijack"
	close(script)
	ts := newClientServerTest(t, mode, HandlerFunc(func(w ResponseWriter, r *Request) {
		plan := <-script
		switch plan {
		default:
			panic("bogus plan; too many requests")
		case "closenotify":
			w.(CloseNotifier).CloseNotify() // discard result
			w.Header().Set("X-Addr", r.RemoteAddr)