Delete socket.upgradeReq when it is no longer needed to reduce memory usage

cc @lpinca

Author: feross

lib/server/parse-websocket.js

@@ -62,5 +62,8 @@ function parseWebSocketRequest (socket, opts, params) {
 
   params.headers = socket.upgradeReq.headers
 
+  // "Free" `socket.upgradeReq` when it is no longer needed to reduce memory usage
+  delete socket.upgradeReq
+
   return params
 }