NodeJs命令提示符窗口立即关闭

这是我的app.js代码。。。。

'use strict';
var createError = require('http-errors');
var express = require('express');
var path = require('path');
var cookieParser = require('cookie-parser');
var logger = require('morgan');
var expressValidator = require('express-validator');
var flash = require('express-flash');
var session = require('express-session');
var bodyParser = require('body-parser');

var mysql = require('mysql');
var connection = require('./lib/db');

var indexRouter = require('./routes/index');
var usersRouter = require('./routes/users');
var customersRouter = require('./routes/customers');

var app = express();

// view engine setup
app.set('views', path.join(__dirname, 'views'));
app.set('view engine', 'pug');

// uncomment after placing your favicon in /public
//app.use(favicon(__dirname + '/public/favicon.ico'));
app.use(logger('dev'));
app.use(bodyParser.json());
app.use(bodyParser.urlencoded({ extended: false }));
app.use(cookieParser());
app.use(express.static(path.join(__dirname, 'public')));

app.use(session({
    secret: '123456cat',
    resave: false,
    saveUninitialized: true,
    cookie: { maxAge: 60000 }
}))

app.use(flash());
app.use(expressValidator());

app.use('/', indexRouter);
app.use('/users', usersRouter);
app.use('/customers', customersRouter);

// catch 404 and forward to error handler
app.use(function (req, res, next) {
    next(createError(404));
});

// error handler
app.use(function (err, req, res, next) {
    // set locals, only providing error in development
    res.locals.message = err.message;
    res.locals.error = req.app.get('env') === 'development' ? err : {};
    // render the error page
    res.status(err.status || 500);
    res.render('error','\n\n');
});
module.exports = app;


app.set('port', process.env.PORT || 3000);

var server = app.listen(app.get('port'), function () {
    debug('Express server listening on port ' + server.address().port);
});