docs: use io.engine.use() with express-session

Related: #4819

examples/express-session-example/index.html

@@ -52,6 +52,10 @@
       socket.on("disconnect", () => {
         ioStatus.innerText = "disconnected";
       });
+
+      socket.on("current count", (count) => {
+        ioCount.innerText = count;
+      });
     </script>
   </body>
 </html>

examples/express-session-example/index.js

@@ -24,6 +24,8 @@ app.post("/incr", (req, res) => {
   const session = req.session;
   session.count = (session.count || 0) + 1;
   res.status(200).end("" + session.count);
+
+  io.to(session.id).emit("current count", session.count);
 });
 
 app.post("/logout", (req, res) => {
@@ -35,37 +37,9 @@ app.post("/logout", (req, res) => {
   });
 });
 
-const io = new Server(httpServer, {
-  allowRequest: (req, callback) => {
-    // with HTTP long-polling, we have access to the HTTP response here, but this is not
-    // the case with WebSocket, so we provide a dummy response object
-    const fakeRes = {
-      getHeader() {
-        return [];
-      },
-      setHeader(key, values) {
-        req.cookieHolder = values[0];
-      },
-      writeHead() {},
-    };
-    sessionMiddleware(req, fakeRes, () => {
-      if (req.session) {
-        // trigger the setHeader() above
-        fakeRes.writeHead();
-        // manually save the session (normally triggered by res.end())
-        req.session.save();
-      }
-      callback(null, true);
-    });
-  },
-});
+const io = new Server(httpServer);
 
-io.engine.on("initial_headers", (headers, req) => {
-  if (req.cookieHolder) {
-    headers["set-cookie"] = req.cookieHolder;
-    delete req.cookieHolder;
-  }
-});
+io.engine.use(sessionMiddleware);
 
 io.on("connection", (socket) => {
   const req = socket.request;

examples/express-session-example/package.json

@@ -10,6 +10,6 @@
   "dependencies": {
     "express": "~4.17.3",
     "express-session": "~1.17.2",
-    "socket.io": "~4.4.1"
+    "socket.io": "^4.7.2"
   }
 }