gistfile1.txt

return new Promise((resolve, reject) => {
        mongoose.connect(DATABASE_URL, err => {
            if (err) {
                return reject(err);
            }
            server = app.listen(port, () => {
                console.log(`Your app is listening on port $ {port}`);
                resolve(server);
            }).on('error', err => {
                reject(err);
            });
        });
    });