Express Serve html files located in app.getAppPath()

Hello everyone
I’m newbie with electron and nodejs and i’m working on my first project
there is a way to serve file located at the same executable location?
this is the project stucture

after launch run script yarn compile && electron-builder and launch my application i get this error
Cannot get /contents/

this is my code

const PORT = 18081;

const app = express();

app.set('port', PORT);

const server = http.createServer(app);
server.listen(PORT, "");

function createMainWindow() {
  const window = new BrowserWindow()

  if (isDevelopment) {


thanks in advanced