[Flask] Not Logged in After Redirect

[alviandk]

I have followed the flask_example with google OAuth2. When I did the authorization, the user successfully made and entered into the database. But after the redirect, the user was not automatically logged in. I combined python-social-auth with flask-security. Can someone help me figure it out where I made a mistake?
This is my implementation in app.py

user_datastore = SQLAlchemyUserDatastore(db, User, Role)
security = Security(app, user_datastore)



engine = create_engine(app.config['SQLALCHEMY_DATABASE_URI'])
Session = sessionmaker(autocommit=False, autoflush=False, bind=engine)
db_session = scoped_session(Session)
app.register_blueprint(social_auth)
init_social(app, db_session)


login_manager = login.LoginManager()
login_manager.login_view = 'security.login'
login_manager.login_message = ''
login_manager.init_app(app)
@login_manager.user_loader
def load_user(userid):
    return User.query.get(int(userid))



@app.before_request
def global_user():
    g.user = login.current_user


@app.teardown_appcontext
def commit_on_success(error=None):
    if error is None:
        db_session.commit()
    else:
        db_session.rollback()

    db_session.remove()


@app.context_processor
def inject_user():
    try:
        return {'user': g.user}
    except AttributeError:
        return {'user': None}


app.context_processor(backends)