chore: add multiple api example (#207)

* chore: add multiple api example
* chore: update README.md

example/multiple/README.md

@@ -0,0 +1,23 @@
+
+# Multiple API feature
+Since swag 1.7.9 we are allowing registration of multiple endpoints into the same server.
+
+Generate documentation for v1 endpoints
+```shell
+swag i -g main.go -dir api/v1 --instanceName v1
+```
+
+
+Generate documentation for v2 endpoints
+```shell
+swag i -g main.go -dir api/v2 --instanceName v2
+```
+
+Run example
+```shell
+    go run main.go
+```
+
+Now you can access the v1 swagger here [http://localhost:8080/swagger/v1/index.html](http://localhost:8080/swagger/v1/index.html) , 
+and v2 swagger here [http://localhost:8080/swagger/v2/index.html](http://localhost:8080/swagger/v2/index.html)
+