Error says: Server running on port 5000 Error: MongooseError: The uri parameter to openUri() must be a string, got "undefined". Make sure the first parameter to mongoose.connect() or mongoose.crea teConnection() is a string. [nodemon] app crashed - waiting for file changes before starting...

This is my server.js:

require ("dotenv").config({path: '../config.env' });
const express = require('express');
const connectDB = require('./config/db');

//Connect DB
connectDB();

const app = express();

app.use(express.json());

app.use('/api/auth', require('./routes/auth'));

const PORT = process.env.PORT || 5000;


const server = app.listen(PORT, () => console.log(`Server running on port ${PORT}`));

process.on("unhandledRejection", (err, promise) => {
    console.log(`Logged Error: ${err}`);
    server.close(() => process.exit(1));
})

This is my db.js:

const mongoose = require('mongoose');

const connectDB = async() => {
      await mongoose.connect(process.env.MONGO_URI, {
            useNewUrlParser: true,
            useCreateIndex: true,
            useUnifiedTopology: true,
            useFindAndModify: true
        });

        console.log("MongoDB connected");
    };

module.exports = connectDB;

And this is my config.env file:

PORT=5000;

MONGO_URI=mongodb://localhost:27017/mernauth