DeprecationWarning: Unhandled promise rejections are deprecated

I am getting this error on my code, and I don't know how to fix it ?

DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.

My code so far:

router.post('/users/*', (req, res) => {
  User.create(new User({
    email: req.body.identity.user_email,
    authUserId: req.body.identity.user_id
  }))
  res.json(console.log("User Created"))
})
router.get('/users/:id', (req, res, next) => {
  User.findOne({authUserId: req.params.id}, (err, userr) => {
    if(err) {
      return next(err);
    } else if (userr) {
      res.json(userr.email);
    } else {
      res.json(null)
    }
  });
});

Can someone help me get rid of this error. Thnx in advance! :)

via Marketingexpert