....
const mongoose=require('mongoose')
const PORT = process.env.PORT || 3000
async function start(){
try{

await mongoose.connect('mongodb://127.0.0.1/test_db')
app.listen(PORT,()=>{
  console.log('Сервер работает. Порт 3000')
})
}catch(e){
console.log(e)
}}
  
start()

{
  "name": "express",
  "version": "1.0.0",
  "main": "index.js",
  "scripts": {
    "start": "node index.js",
    "dev": "nodemon index.js"
  },
  "keywords": [],
  "author": "",
  "license": "ISC",
  "dependencies": {
    "express": "^4.16.4",
    "express-handlebars": "^3.0.2",
    "mongodb": "^4.9.1",
    "mongoose": "^6.5.5",
    "uuid": "^3.3.2"
  },
  "devDependencies": {
    "nodemon": "^1.18.11"
  },
  "description": ""
}