fix: worker may block by worker_chan

pkg/appsrv/appsrv.go

@@ -268,7 +268,7 @@ func (app *Application) defaultHandle(w http.ResponseWriter, r *http.Request, ri
 		hand, ok := handler.(*SHandlerInfo)
 		if ok {
 			fw := newResponseWriterChannel(w)
-			worker := make(chan *SWorker)
+			currentWorker := make(chan *SWorker, 1) // make it a buffered channel
 			to := hand.FetchProcessTimeout(r)
 			if to == 0 {
 				to = app.processTimeout
@@ -320,13 +320,13 @@ func (app *Application) defaultHandle(w http.ResponseWriter, r *http.Request, ri
 					} // otherwise, the task has been timeout
 					fw.closeChannels()
 				},
-				worker,
+				currentWorker,
 				func(err error) {
 					httperrors.InternalServerError(&fw, "Internal server error: %s", err)
 					fw.closeChannels()
 				},
 			)
-			runErr := fw.wait(ctx, worker)
+			runErr := fw.wait(ctx, currentWorker)
 			if runErr != nil {
 				switch runErr.(type) {
 				case *httputils.JSONClientError:

pkg/appsrv/response.go

@@ -100,7 +100,12 @@ func (w *responseWriterChannel) wait(ctx context.Context, workerChan chan *SWork
 	stop := false
 	for !stop {
 		select {
-		case worker = <-workerChan:
+		case curWorker, more := <-workerChan:
+			if more {
+				worker = curWorker
+			} else {
+				// ignore, worker is responsible for close the channel
+			}
 		case <-ctx.Done():
 			// ctx deadline reached, timeout
 			if worker != nil {

pkg/appsrv/workers.go

@@ -83,6 +83,9 @@ func (worker *SWorker) run() {
 			task := req.(*sWorkerTask)
 			if task.worker != nil {
 				task.worker <- worker
+				// worker channel is buffered
+				// close the worker channel
+				close(task.worker)
 			}
 			execCallback(task)
 		} else {