我很确定我的代码是正确的

index.js

//...
const winston      = require('winston');
const express      = require('express');
const app          = express();


require('./startup/logging');
require('express-async-errors');
require('./startup/routes')(app);
require('./startup/db').connect();
require('./startup/config')();
require('./startup/validation')();
require('./startup/prod')(app);

app.get('/', function(req, res, next){
    res.status(200).send('Welcome!');
});

//error handler

app.use(errorHandler);


const port   = process.env.PORT || 3000

const server = app.listen(port, () => winston.info(`listening on port ${port}`))

module.exports = server

和parkage.json

{
  //...
  "main": "index.js",
  "scripts": {
   //...
    "start": "node index.js"
  },
  "engines": {
    "node": "10.x",
    "npm": "6.x"
  },

  //....
}

我部署到Heroku，我收到了这个错误 ...heroku[web.1]: Process exited with status 0 ...heroku[web.1]: State changed from starting to crashed

它最初工作但突然停止我已按照我在网上找到的所有说明但没有任何工作可以有人帮忙吗？

javascript node.js express heroku npm