Cannot return value with asyn function and setTimeout on node.js

I have a class which make a query into my db to get all configKeys and configValue for the website.

I have to immediatly set the value of application.config to the value returned by the callback of new Config

This is the master file -> application.js

var Application = require('Class').create({
initialize: function(rootPath) {
    this.rootPath         = rootPath;
    this.websitePath      = this.rootPath;
    this.websiteUrl       = null;
    this.adminPath        = './admin/';

    // Définition des chemins globaux
    this.globalPath       = this.rootPath + 'global/';
    this.modulePath       = this.globalPath + 'modules/';
    this.dbModulePath     = this.modulePath + 'db/';
    this.odbcPath         = this.globalPath + 'odbc/';

    // Définition des autres dossiers
    this.modelPath        = this.websitePath + 'models/';
    this.skinPath         = this.websitePath + 'skins/';
    this.viewPath         = this.skinPath + 'views/';

    // Définition des principaux fichiers
    this.commonFile       = this.modulePath + 'common.js';
    this.configFile       = this.modulePath + 'configuration.js';
    this.odbc             = this.odbcPath + 'mongoose.js';
    this.securityFile     = this.modulePath + 'security.js';

    // Définition des controllers
    this.modelFile        = this.globalPath + 'model.controller.js';

    // Définition des modules
    this.adminApplication = require(this.adminPath + 'application.js');
    this.cookieParser     = require('cookie-parser');
    this.express          = require('express');
    this.fs               = require('fs');
    this.swig             = require('swig');
},

loadConfig: function() {
    var self = this;

    // Initialisation de la configuration
    if ( this.fs.existsSync(this.configFile) ) {
        var Config  = require(this.configFile);
        new Config(function(config) {
            if ( config ) {
                self.config     = config;
                self.websiteUrl = self.config.WebsiteUrl;
            }
        });

        console.log(this.config); //return undefined because of async...
        debugger;
    }
    else {
        throw 'Cannot find the config file, please check that the file exists!\n';
    }

    // Initialisation de la class Common
    if ( this.fs.existsSync(this.commonFile) ) {
        var Common  = require(this.commonFile);
        this.common = new Common();
    }
    else {
        throw 'Cannot find the common file, please check that the file exists!\n';
    }

    // ODBC
    if ( !this.fs.existsSync(this.odbc) ) {
        throw 'Cannot find any ODBC, please check that the file exists!\n';
    }

    // Initialisation d'express
    this.app = this.express();

    this.app.set('type', 'front');
    this.app.set('case sensitive routing', true);

    // Config SWIG
    this.app.engine('html', this.swig.renderFile);
    this.app.set('view engine', 'html');
    this.app.set('views', this.viewPath);
    this.app.set('view cache', false);
    this.swig.setDefaults({cache: false});

    // On récupère les cookies sur chaque page
    this.app.use(this.cookieParser());
    // On déclare le dossier public accessible partout depuis le site
    this.app.use('/skins', this.express.static(this.skinPath));

    // Initialisation du Model Controller
    if ( this.fs.existsSync(this.modelFile) ) {
        var ModelController  = require(this.modelFile);
        this.modelController = new ModelController(this);
    }
    else {
        throw 'Cannot find the Front Model Controller, please check that the file exists!\n';
    }
},

start: function() {
    // On écoute sur le serveur au port 7777
    this.app.listen(7777, 'localhost');
}
});

module.exports = Application;

In application.js, I call configuration.js by doing 'new Config(function(config){..}' in the loadConfig method of Application.js

now this is the configuration.js file

var Configuration = require('Class').create({
initialize: function(callback) {
    this.host        = 'localhost';
    this.port        = 27017;
    this.database    = 'sgc';
    this.user        = 'xxx';
    this.pass        = 'xxx';

    this.loadConfig(callback);
},

loadConfig: function(callback) {
    var ODBC         = require('../odbc/mongoose.js');
    this.db          = new ODBC(this);

    var Configs      = require('./db/configs.js');
    this.configs     = new Configs(this.db);

    var queryResults = 0;
    var self         = this;


    this.db.find(self.configs.model, null, null, function(results) {
        for ( var rows in results ) {
            self[results[rows].ConfigKey] = results[rows].ConfigValue;
            queryResults                  = rows;
        }

        self.db.close();
        callback(self);
    });

    // db.find(this.configs.model, null, null, function(results) {
    //  for ( var rows in results ) {
    //      self[results[rows].ConfigKey] = results[rows].ConfigValue;
    //      queryResults                  = rows;
    //  }
    //  db.close();
    // });

    // function waitValues() {
    //  if ( queryResults > 0 ) {
    //      // console.log(self);
    //      // return self;
    //      callback(self);
    //      // result(queryResults);
    //  }
    //  else {
    //      setTimeout(waitValues, 100);
    //  }
    // }

    // waitValues();
}
});

module.exports = Configuration;

I have to use application.config later in the project because it must contain all the values found in the database (the values for the configuration of my website)