Express Web-Page not loading Mongoose throwing error

Question

apparently I am trying to make a registration system which is failing the local server web-page isn't loading,
my user data is not been sent to MongoDB and also VS Code terminal is throwing out errors at me

VS Code ERROR :

(node:3188) UnhandledPromiseRejectionWarning: MongooseError: Operation `users.insertOne()` buffering timed out after 10000ms
    at Timeout.<anonymous> (E:\Projects\Applications\chatter\node-rest-api\node_modules\mongoose\lib\drivers\node-mongodb-native\collection.js:185:20)
    at listOnTimeout (internal/timers.js:554:17)
    at processTimers (internal/timers.js:497:7)
(Use `node --trace-warnings ...` to show where the warning was created)
(node:3188) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). To terminate the node process on unhandled promise rejection, use the CLI flag `--unhandled-rejections=strict` (see https://nodejs.org/api/cli.html#cli_unhandled_rejections_mode). (rejection id: 3)
(node:3188) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.

MY CODE GOES HERE :

1. AUTH.JS

   const User = require("../models/User");
   
   // REGISTER 
   router.get("/register", async (req, res) => {
       const user = await new User ({
           username: "john",
           email: "[email protected]",
           password: "123456"
       })
   
       await user.save();
       res.send("oK")
   });
   
   module.exports = router;
   
   

2. INDEX.JS

   const application = express();
   const mongoose = require("mongoose");
   const dotenv = require("dotenv");
   const helmet = require("helmet");
   const morgan = require("morgan");
   const userRoute = require("./routes/users");
   const authRoute = require("./routes/auth");
   
   dotenv.config();
   
   mongoose.connect(process.env.MONGO_URL, {useNewUrlParser: true, useUnifiedTopology: true}, () => {
       console.log("connected to MongoDB");
   });
   
   // middleware 
   application.use(express.json());
   application.use(helmet());
   application.use(morgan("common"));
   
   application.use("/api/users", userRoute);
   application.use("/api/auth", authRoute);
   
   application.listen(8800, () => {
       console.log("backend server has been setup and in running!");
   });
   
   

I initially in /api/auth after changing my code i needed to change URL to /api/auth/register but it is taking forever to load,

also the following is shown by Developer Tools (Ctrl + Shift + I) ERROR IN CONSOLE