req.user undefined when calling cloud function with sessionToken after about a week #3299

app.use(function(req, res, next) {
    if (req.session && req.session.token) {
        Parse.Cloud.httpRequest({
          url: serverURL + '/users/me',
          headers: {
            'X-Parse-Application-Id': process.env.APP_ID,
            'X-Parse-REST-API-Key': process.env.REST_API_KEY,
            'X-Parse-Session-Token': req.session.token
          }
        }).then(function (httpResponse) {
          req.user = httpResponse.data;
          next();
        }, function(httpError){
          req.session = null;
          req.user = null;
          next();
        })
    } else {
        next();
    }
});

app.post('/login', function (req, res) {
    var redirect = req.body.redirect;
    var role = req.body.role;
    var username = req.body.username.toLowerCase();
    var password = req.body.password;
    Parse.User.logIn(username, password).then(function(user){
      req.session.token = user.getSessionToken();  // pass session token to web client
      res.send({redirect: '/' + redirect + "?role=" + role});
    }, function(error){
      res.status(401).send("Invalid email and password combination.");
    })
})

  app.post("/get-todos", function(req, res) {
    console.log(":::get-todos called by " + req.user.id + " with token " + req.session.token);
    Parse.Cloud.run("getTodos", {
      <some params>
    }, {
      sessionToken: req.session.token
    }).then(function(payload){
      res.status(200).send(payload);
    }, function(error) {
      res.status(500).send(error);
    })
  })

Parse.Cloud.define("getTodos", function(request, response) {
    if (!request.user) return response.error("you are not a user") // this becomes undefined after server is running for about a week.
    var todoQuery = new Parse.Query("Todo");
    todoQuery.equalTo("user", request.user);
    todoQuery.find().then(function(results){
        response.success(results)
    }, function(error){
        response.error(error);
    })
})