express, and mongoose api post socket hang up

I’m sending a post req via Postman to localhost:5000/api/auth/register, and the socket keeps hanging up on me. What am I missing? Thanks in advance!
(I’m using mongoDB’s free cluster)

{
    "username": "ChronoKross",
    "email": "email@gmail.com",
    "password": "123"
}

here is my schema:

const mongoose = require("mongoose");

const UserSchema = new mongoose.Schema({
    username:{
        type: String,
        required: true,
        unique: true
    },
    email:{
        type: String,
        required: true,
        unique: true
    },
    password:{
        type: String,
        required: true
    },
    profilePicture:{
        type: String,
        default: "",
    }, 
},
    { timestamps: true }
);

module.exports = mongoose.model("User", UserSchema);

here is my route:

const router = require("express").Router();
const User = require("../models/User");

//REGISTER
router.post("/register", async (req, res)=> {
    try{
        const newUser = new User({
            username: req.body.username,
            email: req.body.email,
            password: req.body.password,
        });

        const user = await newUser.save();
        res.status(200).json(user);

    } catch(err){
        res.status(500).json(err);
    }
})

//LOGIN

module.exports = router;

and here is my index.js:

const express = require('express');
const app = express();
const dotenv = require("dotenv");
const mongoose = require("mongoose");
const authRoute = require("./routes/auth");

dotenv.config();
app.use(express.json);

mongoose
    .connect(process.env.MONGO_URL)
    .then(console.log("Connected to MONGODB"))
    .catch(err=>console.log(err));

    app.use("/api/auth", authRoute);


app.listen("5000", () => {
    console.log("Backend is running.");
})

Im following an online guide, and I can’t find anything that I have done wrong. I’m using NodeJs, ExpressJs, MongooseJs, and Postman. If you need any additional information please let me know. — I was just about to embarrassed to post this question lol…

>Solution :

express.json is a function, also try to start the server after the DB has successfully connected:

app.use(express.json());

app.use("/api/auth", authRoute);

mongoose
    .connect(process.env.MONGO_URL)
    .then(() => {
      console.log("Connected to MONGODB")
      
      app.listen("5000", () => {
        console.log("Backend is running.");
      })
    })
    .catch(err=>console.log(err));