Express 4 session issues

  node.js, question

Ireq.session.UserID = _id;After setting up the session. In another route cannot be taken out, is for what? Ask for advice.

router.get('/', function(req, res, next) {
 var _id = req.query.UserID;
 if(_id){
 req.session.UserID = _id;
 bracket
 res.render('index', { title: 'Express' });
 });
router.get('/about', function(req, res, next) {
 console.log(req,session.UserID);
 res.render('about')
 })

console.log(req,session.UserID);Output, the results page shows sessioninsnot defined

console.log(req,session.UserID);
Friends, you putFull stopWrite,The