reorganization of _examples and add some new examples such as iris+groupcache+mysql+docker

Former-commit-id: ed635ee95de7160cde11eaabc0c1dcb0e460a620

_examples/http-server/graceful-shutdown/default-notifier/main.go

@@ -0,0 +1,34 @@
+package main
+
+import (
+	stdContext "context"
+	"time"
+
+	"github.com/kataras/iris/v12"
+)
+
+// Before continue:
+//
+// Gracefully Shutdown on control+C/command+C or when kill command sent is ENABLED BY-DEFAULT.
+//
+// In order to manually manage what to do when app is interrupted,
+// We have to disable the default behavior with the option `WithoutInterruptHandler`
+// and register a new interrupt handler (globally, across all possible hosts).
+func main() {
+	app := iris.New()
+
+	iris.RegisterOnInterrupt(func() {
+		timeout := 10 * time.Second
+		ctx, cancel := stdContext.WithTimeout(stdContext.Background(), timeout)
+		defer cancel()
+		// close all hosts
+		app.Shutdown(ctx)
+	})
+
+	app.Get("/", func(ctx iris.Context) {
+		ctx.HTML(" <h1>hi, I just exist in order to see if the server is closed</h1>")
+	})
+
+	// http://localhost:8080
+	app.Listen(":8080", iris.WithoutInterruptHandler)
+}