add a new 'overview' MVC example

Former-commit-id: f73cbf6010595c639f6c5b5119e2ec41bc9802a5

_examples/mvc/overview/controller/greet_controller.go

@@ -0,0 +1,23 @@
+package controller
+
+import (
+	"app/model"
+	"app/service"
+)
+
+// GreetController handles the index.
+type GreetController struct {
+	Service service.GreetService
+	// Ctx iris.Context
+}
+
+// Get serves [GET] /.
+// Query: name
+func (c *GreetController) Get(req model.Request) (model.Response, error) {
+	message, err := c.Service.Say(req.Name)
+	if err != nil {
+		return model.Response{}, err
+	}
+
+	return model.Response{Message: message}, nil
+}