Adding required libraries and modules for user authentication, adding serializing and de-serializing the user information to the session. https://github.com/AndrejGajdos/auth-flow-spa-node-react/blob/master/script/controllers/auth.js

auth.js

const bcrypt = require('bcrypt');
const passport = require('koa-passport');
const FacebookStrategy = require('passport-facebook').Strategy;
const LocalStrategy = require('passport-local').Strategy;
const config = require('../serverConfig');
const { db } = require('../server');
const { promisify } = require('util');

const getAsync = promisify(db.get).bind(db);

passport.serializeUser((user, done) => {
  done(null, user.id);
});

passport.deserializeUser(async (id, done) => {
  try {
    let user = null;
    await getAsync('usersMockDatabase').then((users) => {
      user = JSON.parse(users).find(currUser => currUser.id === id);
    });
    if (user) {
      done(null, user);
    } else {
      done(null, false);
    }
  } catch (err) {
    done(err);
  }
});