Node Js, Async Js, Listener must be a function

Question

Below is the output log of the code below that, I don't know why it is throwing the error, I'm think the numbers at the end of the lines are line number:char number, I'll post some key line numbers in with the code.

for some reason not working
series complete

events.js:171
throw TypeError('listener must be a function');
^ TypeError: listener must be a function
at TypeError ()
at NativeConnection.EventEmitter.once (events.js:171:11)
at /home/melman/Documents/Git/angular-test/server.js:39:24
at /home/melman/Documents/Git/angular-test/node_modules/async/lib/async.js:5 48:21
at /home/melman/Documents/Git/angular-test/node_modules/async/lib/async.js:2 24:13
at iterate (/home/melman/Documents/Git/angular-test/node_modules/async/lib/a
sync.js:131:13)
at async.eachSeries (/home/melman/Documents/Git/angular-test/node_modules/as
ync/lib/async.js:147:9)
at _asyncMap (/home/melman/Documents/Git/angular-test/node_modules/async/lib
/async.js:223:9)
at Object.mapSeries (/home/melman/Documents/Git/angular-test/node_modules/as
ync/lib/async.js:213:23)
at Object.async.series (/home/melman/Documents/Git/angular-test/node_modules
/async/lib/async.js:546:19)

28: var serverConfiguration = {
    init: function (){
30:       var self = this;

        async.series([
            function (callback) {
                // connect to the db
                db.connect('mongodb://localhost/piautomation');

                var dbConn = db.connection;
                dbConn.on('error', console.error.bind(console, 'connection error:'));
                dbConn.once('open', callback(null));
40:         },
            function (callback) {
                console.log('Configure the db');
                self.models = require('./server/config/mongoose')(db); // setup the db with the models and schemas
                callback(null);
            },
            function (callback) {
                console.log("Start creating models");
                self.newsApi = require('./server/api/news')(self.models.News); // pass the news api the News model
                callback(null);
50:         },
            function (callback) {
                console.log("configure routes");
                require('./server/config/routes')(app, self.newsApi, clientDir, callback); // set up the routes with the model api's functions
            },
            function (callback) {
                console.log("http server created");
                var server = http.createServer(app);
                console.log("starting reload");
                reload(server, app);
60:             console.log("start server listen");
                // if we have successful db connection, allow the rest of the app to start up
                server.listen(app.get('port'), function(){
                    console.log("Web server listening in %s on port %d", colors.red(process.env.NODE_ENV), app.get('port'));
                    callback(null);
                });
                console.log("for some reason not working");
                callback(null);
            }
        ], function () {
70:         console.log("series complete");
        });
    }
}.init();

Answer 1

try changing line 39 from

dbConn.once('open', callback(null));

to

dbConn.once('open', callback);