function handleAuth(err, user) {
    if (err) {
      return redirectUser(err, user);
    }
    if (req.session && typeof req.session.save === 'function') {
      return req.session.save((err) => {
        redirectUser(err, user);
      });
    }
    return redirectUser(err, user);
  }
A custom passport authenticate handler to save session before redirect
@param {*} err
@param {*} user
@param {*} info