chore: add multiple api example (#207)

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

example/multiple/api/v2/main.go

@@ -0,0 +1,25 @@
+package v2
+
+import (
+	"github.com/gin-gonic/gin"
+)
+
+// @title Swagger Example API
+// @version 2.0
+// @description This is a sample server.
+// @termsOfService http://swagger.io/terms/
+
+// @contact.name API Support
+// @contact.url http://www.swagger.io/support
+// @contact.email support@swagger.io
+
+// @license.name Apache 2.0
+// @license.url http://www.apache.org/licenses/LICENSE-2.0.html
+
+// @BasePath /v2
+
+func Register(router *gin.Engine) {
+	v2 := router.Group("v2")
+
+	v2.GET("/books", GetBooks)
+}