panic(fmt.Sprintf("httptest: failed to listen on a port: %v", err))
		}
	}
	return l
}

// When debugging a particular http server-based test,
// this flag lets you run
//
//	go test -run='^BrokenTest$' -httptest.serve=127.0.0.1:8000
//
// to start the broken server so you can interact with it manually.
// We only register this flag if it looks like the caller knows about it