node-async-await.js

const authenticateUser = async function(req, res, next) {
  try {
    let user = await User.findOne({ username: req.body.username });

    if (user) {
      let isPasswordMatch = await user.verifyPassword(req.body.password);

      if (isPasswordMatch) {
        let token = await issueToken(user._id);
        res.status(200).send(token);
        return;
      }
    }
    res.status(401).send();
  } catch (err) {
    next(err);
  }
}