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

Former-commit-id: ed635ee95de7160cde11eaabc0c1dcb0e460a620

_examples/http-server/custom-httpserver/multi/main.go

@@ -0,0 +1,47 @@
+package main
+
+import (
+	"net/http"
+
+	"github.com/kataras/iris/v12"
+)
+
+func main() {
+	app := iris.New()
+
+	app.Get("/", func(ctx iris.Context) {
+		ctx.Writef("Hello from the server")
+	})
+
+	app.Get("/mypath", func(ctx iris.Context) {
+		ctx.Writef("Hello from %s", ctx.Path())
+	})
+
+	// Note: It's not needed if the first action is "go app.Run".
+	if err := app.Build(); err != nil {
+		panic(err)
+	}
+
+	// start a secondary server listening on localhost:9090.
+	// use "go" keyword for Listen functions if you need to use more than one server at the same app.
+	//
+	// http://localhost:9090/
+	// http://localhost:9090/mypath
+	srv1 := &http.Server{Addr: ":9090", Handler: app}
+	go srv1.ListenAndServe()
+	println("Start a server listening on http://localhost:9090")
+
+	// start a "second-secondary" server listening on localhost:5050.
+	//
+	// http://localhost:5050/
+	// http://localhost:5050/mypath
+	srv2 := &http.Server{Addr: ":5050", Handler: app}
+	go srv2.ListenAndServe()
+	println("Start a server listening on http://localhost:5050")
+
+	// Note: app.Run is totally optional, we have already built the app with app.Build,
+	// you can just make a new http.Server instead.
+	// http://localhost:8080/
+	// http://localhost:8080/mypath
+	app.Listen(":8080") // Block here.
+}