diff --git a/co/koa.md b/co/koa.md
index dca95c5..8f2c2b0 100644
--- a/co/koa.md
+++ b/co/koa.md
@@ -37,7 +37,7 @@
                 }
                 //执行第一个中间件
                 yield prev;
-            })();
+            });
         }
     };