通过Post编辑的ExpressJS会话Cookie不保存

Question

我在这里很困惑。每当有get请求时我都可以编辑和读取cookie，但是如果我通过帖子编辑cookie，则不会保存：

    // GET    
    exports.index = function(req, res) {
     req.session.teststore = "This is set from a GET";
     console.log('Reading from a cookie..... :::' , req.session.teststore);
     res.render('index');
    };   

    // Outputs: 'Reading from a cookie..... ::: , 'This is set from a GET'


    exports.page2 = function(req, res) {
     console.log('Reading from a cookie..... :::' , req.session.teststore);
     res.render('page2');
     res.end();
    };

    // Outputs: 'Reading from a cookie..... ::: , 'This is set from a GET'


   //POST
   exports.update = function (req,res) {
    console.log('the value of this cookie is ::: ' , req.session.teststore);
    req.session.teststore = "This is set from a POST"; 
    console.log('the value of this cookie is ::: ' , req.session.teststore);};
    res.send(200);
   }

   // Outputs: 
   the value of this cookie is :::  This is set from a GET
   the value of this cookie is :::  This is set from a POST

    //GET
    exports.page3 = function(req, res) {
     console.log('Reading from a cookie..... :::' , req.session.teststore);
     res.render('page3');
     res.end();
    };

    // Outputs: 'Reading from a cookie..... ::: , 'This is set from a GET'

我很困惑因为我希望第3页的GET请求看到cookie已更新。为了确认，cookie只在'/'索引请求中设置了一次，然后仅在Post请求中更改。

有什么想法吗？