ptb-be/config/db.js

const mongoose = require('mongoose')
require('dotenv').config()

const main = () => {
  mongoose.connect(process.env.MONGO_URL, {
    useNewUrlParser: true,
    useUnifiedTopology: true,
  })

  const db = mongoose.connection
  db.on('error', console.error.bind(console, 'MongoDB connection error:'))
  db.once('open', function () {
    console.log('Connection Successful!')
  })
}

module.exports = main