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))
	})

	log.Fatal(http.ListenAndServe(":8080", nil))