feat: add custom error page for unmatched routes

main.go

@@ -30,6 +30,14 @@ func main() {
 	r.HandleFunc("/{id}-lyrics", lyricsHandler)
 	r.HandleFunc("/images/{filename}.{ext}", proxyHandler)
 	r.PathPrefix("/static/").Handler(http.StripPrefix("/static/", http.FileServer(http.Dir("static"))))
+	r.NotFoundHandler = http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusNotFound)
+		render("error", w, map[string]string{
+			"Status": "404",
+			"Error":  "page not found",
+		})
+
+	})
 
 	server := &http.Server{
 		Handler:      r,