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

Former-commit-id: ed635ee95de7160cde11eaabc0c1dcb0e460a620

_examples/http-server/iris-configurator-and-host-configurator/main.go

@@ -0,0 +1,28 @@
+package main
+
+import (
+	"github.com/kataras/iris/v12"
+)
+
+func main() {
+	app := iris.New()
+
+	app.ConfigureHost(func(host *iris.Supervisor) { // <- HERE: IMPORTANT
+		// You can control the flow or defer something using some of the host's methods:
+		// host.RegisterOnError
+		// host.RegisterOnServe
+		host.RegisterOnShutdown(func() {
+			app.Logger().Infof("Application shutdown on signal")
+		})
+	})
+
+	app.Get("/", func(ctx iris.Context) {
+		ctx.HTML("<h1>Hello</h1>\n")
+	})
+
+	app.Listen(":8080", iris.WithoutServerError(iris.ErrServerClosed))
+
+	/* There are more easy ways to notify for global shutdown using the `iris.RegisterOnInterrupt` for default signal interrupt events.
+	You can even go it even further by looking at the: "graceful-shutdown" example.
+	*/
+}