Unknown Authentication Facebook Strategy - PassportJS - node.js

Question

I've a issue with PassportJS. It displays this message and I can't understand where I'm doing wrong:
{"message":"Unknown authentication strategy \"facebook\"","error":{}}
GET /auth/facebook 500 0.505 ms - 69
Credentials are hardcoded for simplicity and learning purpose. Passport and Passport-Facebook are installed.
auth/index.js
var passport = require('passport');
var FacebookStrategy = require('passport-facebook').Strategy;
var User = require('../modules/user');
module.exports = function(){
passport.use( new FacebookStrategy({
clientID: "secret",
clientSecret : "secret",
callbackURL : "secret"
},
function(accessToken, refreshToken, profile, done) {
User.findOne({ email: profile.emails[0].value }, function (err, user) {
if (err) { return done(err) }
if (!user) {
user = new User({
firstname: profile.name.givenName,
lastname: profile.name.familyName,
email: profile.emails[0].value,
providers: {
facebook: {
id: profile.id,
access_token: accessTOken,
display_name: displayName,
picture: "http://graph.facebook.com/"+profile.id+"/picture?type=square"
}
}
})
user.save(function (err) {
if (err) console.log(err)
return done(err, user)
})
}
else {
return done(err, user)
}
})
}
));
};
routes/auth.js
var express = require('express');
var router = express.Router();
var passport = require('passport');
router.get('/facebook', passport.authenticate('facebook'), function(res, res){});
router.get('/facebook/callback', passport.authenticate('facebook'), function(res, res){});
module.exports = router;
app.js
const express = require('express');
const path = require('path');
const logger = require('morgan');
const cookieParser = require('cookie-parser');
const bodyParser = require('body-parser');
const mongoose = require('mongoose');
const passport = require('passport');
const auth = require('./routes/auth');
const app = express();
mongoose.connect('mongodb://localhost:auth/auth');
app.use(logger('dev'));
app.use(bodyParser.json());
app.use(bodyParser.urlencoded({ extended: false }));
app.use(cookieParser());
app.use(passport.initialize());
app.use('/auth', auth);
// catch 404 and forward to error handler
app.use(function(req, res, next) {
var err = new Error('Not Found');
err.status = 404;
next(err);
});
// error handlers
// development error handler
// will print stacktrace
if (app.get('env') === 'development') {
app.use(function(err, req, res, next) {
res.status(err.status || 500);
res.json({
message: err.message,
error: err
});
});
}
// production error handler
// no stacktraces leaked to user
app.use(function(err, req, res, next) {
res.status(err.status || 500);
res.json({
message: err.message,
error: {}
});
});
module.exports = app;
SOLUTION:
As suggested, I just add this line before app.use(passport.initialize());
app.js
require('./auth')(passport);

Answer 1

SOLUTION:
As suggested, I just add this line before app.use(passport.initialize());
app.js
require('./auth')(passport);