问题似乎是与mongoose和mongodb包，因为它的工作正常时

mongoose.connect('mongodb+srv://mydb:<password>@cluster0.w1opr.mongodb.net/test?retryWrites=true&w=majority');

它也可以在www.example.com云环境中正常工作repl.it，这是我的代码

var express = require('express');
var ejs = require('ejs');
var app = express();
var bodyParser = require('body-parser');
var mongoose = require('mongoose');
mongoose.connect('mongodb+srv://mydb:<password>@cluster0.w1opr.mongodb.net/test? 
retryWrites=true&w=majority');
app.set('view engine','ejs')
app.use(bodyParser.urlencoded({extended: true}));
.
.
.
app.listen(3000,function(){
console.log('Server is running on port 3000');
});