App.js

export default class App {
    constructor (services) {
        this.services = services;
    }

    start () {
        const { express, db } = this.services;

        if (!db.models) {
            db.loadModels(this.services);
        }

        express.set('services', this.services);

        express.use(async (request, response, next) => {
            const { User } = db.models;
            
            // This is pseudocode, we have a session service that reads user it from JWT token
            response.locals.user = await User.findByPk(request.headers['X-User-Id']);

            next();
        });

        return express;
    }
}