Fix memory leak

lib/cors-anywhere.js

@@ -142,11 +142,27 @@ function onProxyResponse(req, res, response) {
           
           req.method = 'GET';
           requestState.location = parseURL(locationHeader);
+
+          // ### Dispose the current proxied request
+          // Verified assumption: When proxy.proxyRequest is called for the first time,
+          //  there are no event listeners on the "req" object.
+
+          // First remove the "end" event, to avoid the req.end() call by node-http-proxy/http-proxy
+          // https://github.com/nodejitsu/node-http-proxy/blob/ebbba73e/lib/node-http-proxy/http-proxy.js#L310-319
+          response.removeAllListeners('end');
+          // Trigger disposal of the reverseProxy
+          // https://github.com/nodejitsu/node-http-proxy/blob/ebbba73e/lib/node-http-proxy/http-proxy.js#L375-L378
+          req.emit('aborted');
+          // Remove all listeners (=events reset to initial state)
+          req.removeAllListeners();
+
+          // Initiate a new proxy request.
           proxyRequest(req, res, proxy);
           // Trigger reverseProxy.end() to initiate the proxy
+          // The event listener is added at the end of HttpProxy.prototype.proxyRequest, synchronously.
+          // https://github.com/nodejitsu/node-http-proxy/blob/ebbba73e/lib/node-http-proxy/http-proxy.js#L407-L415
           req.emit('end');
 
-          response.end();
           // The proxyResponse event is wrapped in a try-catch, throwing an error
           // prevents the response from being passed to the client.
           throw new Error('Prevent current response from being passed through.');