连接到Mlab时出错

Question

我正在运行这个节点应用程序，当我用我的mongodb在本地运行时，它运行正常，但是在尝试连接到Mlab时，但我不断得到一些奇怪的错误，我无法弄清楚错误在哪里

错误信息：

[nodemon] starting `node index.js`
Error connecting to mongodb!
[nodemon] clean exit - waiting for changes before restart

index.js

const   con            = require('./con');

const mongoose = require('mongoose');

  mongoose.Promise = con.mongoose.Promise;

  mongoose.connect(con.mongoose.connection)
      .then(() => {
          console.log('Connected to mongodb!');
          require('./app.js');
      })
      .catch(err => {
          console.log('Error connecting to mongodb!');;                                                       
      });

con.js：

module.exports = {
    port: process.env.NODE_PORT || 8080,
    mongoose: {
        Promise: require('bluebird'), //mongoose promise library
        //connection: 'mongodb://localhost:27017/mmmmm',
    mongoose.createConnection(''mongodb://[username:password@]host1');
    }
};

这是我的app.js：

const   express           = require("express"),
        compress          = require("compression"),
        bodyParser        = require("body-parser"),
        cookieParser      = require("cookie-parser"),
        mongoose          = require("mongoose");
        session           = require("express-session"),
        bcrypt            = require("bcrypt"),
        logger            = require("morgan"),
        config            = require('./con');

    const app = express();
    app.enabled('trust proxy');

    app.use(logger('dev'));
    app.use(compress());

    app.use(bodyParser.urlencoded({ extended: true }));
    app.use(express.static("public"));
    app.use(bodyParser.json());
    app.use(cookieParser());      

    app.use(function(req, res, next){
        if (req.session && req.session.userId)
        req.isLoggedIn = true;
        else
        req.isLoggedIn = false;
        next();
        });

        app.use('/', require('./routes/router'));

app.listen(config.port, () => {
    utils.info('Express server listening on port ' + con.port);
    utils.info('http://localhost:' + con.port);
});

我也尝试过：

module.exports = {
    port: process.env.NODE_PORT || 8080,
    mongoose: {
        Promise: require('bluebird'), //mongoose promise library
    },
   url : 'mongodb://[username:password@]host1'
};

请有人帮助我，我已经爬了SO，但没有解决方案。

谢谢