Use custom express webserver with Botkit

bot.js

var Botkit = require('botkit');

// Create the Botkit controller, which controls all instances of the bot.
var controller = Botkit.facebookbot({
    debug: true,
    verify_token: process.env.verify_token,
    access_token: process.env.page_token,
});
// Set up an Express-powered webserver to expose oauth and webhook endpoints
// We are passing the controller object into our express server module
// so we can extend it and process incoming message payloads 
var webserver = require('./express_webserver.js')(controller);

webhook_route.js

module.exports = function(webserver, controller) {
    // Receive post data from fb, this will be the messages you receive 
    webserver.post('/facebook/receive', function(req, res) {

        // respond to FB that the webhook has been received.
        res.status(200);
        res.send('ok');

        var bot = controller.spawn({});

        // Now, pass the webhook into be processed
        controller.handleWebhookPayload(req, res, bot);
    });
    // Perform the FB webhook verification handshake with your verify token 
    webserver.get('/facebook/receive', function(req, res) {
        if (req.query['hub.mode'] == 'subscribe') {
            if (req.query['hub.verify_token'] == controller.config.verify_token) {
                res.send(req.query['hub.challenge']);
            } else {
                res.send('OK');
            }
        }
    });
}

webserver.js

var express = require('express');
var bodyParser = require('body-parser');
var querystring = require('querystring');

module.exports = function(controller, bot) {
    
    var webserver = express();
    webserver.use(bodyParser.json());
    webserver.use(bodyParser.urlencoded({ extended: true }));

    webserver.use(express.static('public'));

    // You can pass in whatever hostname you want as the second argument
    // of the express listen function, it defaults to 0.0.0.0 aka localhost 
    webserver.listen(process.env.PORT || 3000,  null, function() {

        console.log('Express webserver configured and listening at ',
            process.env.HOSTNAME || 'http://localhost/' + ':' + process.env.PORT || 3000);

    });
    // Register our routes, in this case we're just using one route
    // for all incoming requests from FB
    // We are passing in the webserver we created, and the botkit
    // controller into our routes file so we can extend both of them 
    require('./webhook_routes.js')(webserver, controller)
  
    controller.webserver = webserver;
    return webserver;
}