Mongodb – how to connect mongo db composs into express.js

i am running express.js inside electron and i am trying to connect mongodb composs to expressjs

when i start my express.js using electron i am getting error in mongodb
i have created the db in mongodb composs here is the error

here is the code for express .js

const express = require("express");
const mongoose = require("mongoose");
const cors = require("cors");

async function startExpressServer() {
  // Connect to MongoDB
  await mongoose.connect("mongodb://localhost:27017/pos", {
    useNewUrlParser: true,
    useUnifiedTopology: true,
  });
  console.log("Connected to MongoDB");

  const expressApp = express();
  expressApp.use(cors());

  expressApp.get("/", (req, res) => {
    res.send("Hello World from Express!");
  });

  return expressApp;
}

module.exports = { startExpressServer };

in main.js i have this code which stats my express app

app.on("ready", async () => {
  // Start the Express server
  const expressApp = await startExpressServer();
  const port = 3001;
  expressApp.listen(port, () => {
    console.log(`Server listening on port ${port}`);
  });

  createMainWindow();
});

this code worked and ran the express app before i added monogo db connetion