优化单元测试代码

utils/jsonrpc2/server_test.go

@@ -301,7 +301,7 @@ func TestConcurrentRequests(t *testing.T) {
 	var wg sync.WaitGroup
 	errCh := make(chan error, workers)
 
-	for i := 0; i < workers; i++ {
+	for i := range workers {
 		wg.Add(1)
 
 		go func(id int) {