gistfile1.js

// 1 - try / catch doesn't work with async codes, so you don't need to use
// 2 - You need to add a callback to be trigered when everything had run

module.exports = {
    createNewUser: function (user, callback){ 
        connection.query('INSERT INTO users (email, first_name, last_name, password) VALUES ("'+user.email+'", "'+user.first_name+'", "'+user.last_name+'", "'+user.password+'")' , function(err, result) {
            // We will pass the error and the result to the function
            callback(err, result);
        });
    }
};