make the output of gin example right (#1598)

examples/http/README.md

@@ -7,8 +7,8 @@ $ go run gin/main.go
 ```
 2、From a different terminal, access the api to see the output:
 ```shell
-$ curl http://127.0.0.1:8000/home
-Hello Gin!
+$ curl http://127.0.0.1:8000/helloworld/gin
+{"welcome":"gin"}
 ```
 
 ## mux
@@ -30,4 +30,4 @@ $ go run static/main.go
 2、Access the following url with your browser:
 ```
 http://127.0.0.1:8000/assets
-```
+```