# Servers

ListenAndServe starts an HTTP server with a given address and handler.
The handler is usually nil, which means to use [DefaultServeMux].
[Handle] and [HandleFunc] add handlers to [DefaultServeMux]:

	http.Handle("/foo", fooHandler)

	http.HandleFunc("/bar", func(w http.ResponseWriter, r *http.Request) {
		fmt.Fprintf(w, "Hello, %q", html.EscapeString(r.URL.Path))
	})

// an error is returned. The provided handler may be nil to use
// [http.DefaultServeMux].
func Serve(handler http.Handler) error {
	req, err := Request()
	if err != nil {
		return err
	}
	if req.Body == nil {
		req.Body = http.NoBody
	}
	if handler == nil {
		handler = http.DefaultServeMux
	}
	rw := &response{
		req:    req,
		header: make(http.Header),

		"net/http.(*Transport).RoundTrip": true,

		// Verify these don't exist:
		"net/http.http2Server":           false,
		"net/http.(*Server).Serve":       false,
		"net/http.(*ServeMux).ServeHTTP": false,
		"net/http.DefaultServeMux":       false,
	}
	for sym, want := range wantSym {
		got := bytes.Contains(out, []byte(sym))
		if !want && got {
			t.Errorf("cmd/go unexpectedly links in HTTP server code; found symbol %q in cmd/go", sym)
		}