Failed to serialize user into session with passportjs and cookie-session

I'm trying to get authentication with Google+ OAuth. To achieve this I'm using passportjs with Google strategy (passport-google-oauth20 module) but I'm stuck in an error while passport tries to serialize the user into a session (using cookie-session).

The error comes after login in the Google site.

The code:

passport.serializeUser((user, done) => {
    console.log('serialize ' + (user.id == undefined ? null : user.id));
    console.log(user);
    return done(null, (user.id == undefined ? null : user.id));
});

passport.deserializeUser((id, done) => {
console.log('dserialize id ' + id);
   db.connect((err, client, don) => {
        if (err) throw err
        client.query('SELECT * FROM "AppUsers" WHERE "googleId" = $1', [id], (err, res) => {
            don();
            if (err) {
               console.log(err.stack);
            } else {
               console.log(res.rows[0]);
               if (res.rows[0]) {return done(null, res.rows[0]);}
               else {return done(null, null);}
            }
        });
    });
});

Edit:

async function checkGoogle(profile) {
    const client = await db.connect();
    try {
        const { rows } = await client.query('SELECT * FROM "AppUsers" WHERE "googleId" = $1', [profile.id]);
        let currentUser = rows[0];
        console.log(currentUser);
        if (currentUser) {
            console.log('in db ' + currentUser.id);
            console.log(currentUser);
            return currentUser;
        } else {
            const { rows } = await client.query('INSERT INTO "AppUsers" ("googleId") VALUES ($1) RETURNING *', [profile.id]);
            let newUser = rows[0];
            console.log('not in db ' + newUser.id);
            console.log(newUser);
            return newUser;
        }
    } catch (error) {
        alert(error);
    } finally {
        client.release();
    }
}

passport.use(
    new GoogleStrategy({
        // options for google strategy
        clientID: keys.google.clientID,
        clientSecret: keys.google.clientSecret,
        callbackURL: '/auth/google/redirect'
    }, (accessToken, refreshToken, profile, done) => {
        // check if user already exists in our own db
        return done(null, checkGoogle(profile));
    })
);

Output: The error screen

Please tell me if you need more information about.

You need to wait for the checkGoogle function to return data by using async/await.

passport.use(
    new GoogleStrategy({
        // options for google strategy
        clientID: keys.google.clientID,
        clientSecret: keys.google.clientSecret,
        callbackURL: '/auth/google/redirect'
    }, async (accessToken, refreshToken, profile, done) => {
        const user = await checkGoogle(profile);
        // check if user already exists in our own db
        return done(null, user);
    })
);