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

Former-commit-id: ed635ee95de7160cde11eaabc0c1dcb0e460a620

_examples/routing/hello-world/main.go

@@ -0,0 +1,42 @@
+package main
+
+import (
+	"github.com/kataras/iris/v12"
+
+	"github.com/kataras/iris/v12/middleware/logger"
+	"github.com/kataras/iris/v12/middleware/recover"
+)
+
+func main() {
+	app := iris.New()
+	app.Logger().SetLevel("debug")
+	// Optionally, add two builtin handlers
+	// that can recover from any http-relative panics
+	// and log the requests to the terminal.
+	app.Use(recover.New())
+	app.Use(logger.New())
+
+	// Method:   GET
+	// Resource: http://localhost:8080
+	app.Handle("GET", "/", func(ctx iris.Context) {
+		ctx.HTML("<h1>Welcome</h1>")
+	})
+
+	// same as app.Handle("GET", "/ping", [...])
+	// Method:   GET
+	// Resource: http://localhost:8080/ping
+	app.Get("/ping", func(ctx iris.Context) {
+		ctx.WriteString("pong")
+	})
+
+	// Method:   GET
+	// Resource: http://localhost:8080/hello
+	app.Get("/hello", func(ctx iris.Context) {
+		ctx.JSON(iris.Map{"message": "Hello Iris!"})
+	})
+
+	// http://localhost:8080
+	// http://localhost:8080/ping
+	// http://localhost:8080/hello
+	app.Listen(":8080")
+}