serverx

var DefaultNotFoundHandler = http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
	var contentType string
	var body []byte
	switch httputil.NegotiateContentType(r, []string{
		"text/html",
		"text/plain",
		"application/json",
	}, "text/html") {
	case "text/plain":
		contentType = "text/plain"
		body = []byte(`Error 404 - The requested route does not exist. Make sure you are using the right path, domain, and port.`)
	case "application/json":
		contentType = "application/json"
		body = page404JSON
	case "text/html":
		fallthrough
	default:
		contentType = "text/html"
		body = page404HTML
	}

	w.Header().Set("Content-Type", contentType+"; charset=utf-8")
	w.WriteHeader(http.StatusNotFound)
	_, _ = w.Write(body)
})