Add README file for http & helloworld examples (#839)

* Add readme for helloworld example.

* Add readme file for http example.

examples/helloworld/README.md

@@ -0,0 +1,10 @@
+# Run the example
+
+1、Compile and execute the server code:
+```shell
+$ go run server/main.go
+```
+2、From a different terminal, compile and execute the client code:
+```shell
+$ go run client/main.go
+```

examples/http/README.md

@@ -0,0 +1,33 @@
+# Run the examples
+
+## gin
+1、Compile and execute the server code:
+```shell
+$ 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!
+```
+
+## mux
+1、Compile and execute the server code:
+```shell
+$ go run mux/main.go
+```
+2、From a different terminal, access the api to see the output:
+```shell
+$ curl http://127.0.0.1:8000/home
+Hello Gorilla Mux!
+```
+
+## static
+1、Compile and execute the server code:
+```shell
+$ go run static/main.go
+```
+2、Access the following url with your browser:
+```
+http://127.0.0.1:8000/assets
+```