update doc

README.md

@@ -170,7 +170,7 @@ public class XXXXInnerServiceImpl implements XXXXService {
 public class Main {
     public static void main(String[] args) {
         ConfigurableApplicationContext context = SpringApplication.run(Main.class, args);
-        DubboContextUtil.setApplicationContext(context.getParent());
+        DubboContextUtil.setApplicationContext(context);
     }
 }
 ```