New Rate Limit middleware (still WIP though)

Former-commit-id: 99e282e4d400c83a56a808212d812cd701e1bcd8

_examples/miscellaneous/ratelimit/main.go

@@ -0,0 +1,47 @@
+package main
+
+import (
+	"time"
+
+	"github.com/kataras/iris/v12"
+	"github.com/kataras/iris/v12/middleware/rate"
+)
+
+func main() {
+	app := newApp()
+	app.Logger().SetLevel("debug")
+
+	app.Listen(":8080")
+}
+
+func newApp() *iris.Application {
+	app := iris.New()
+
+	// Register the rate limiter middleware at the root router.
+	//
+	// Fist and second input parameters:
+	//	  Allow 1 request per second, with a maximum burst size of 5.
+	//
+	// Third optional variadic input parameter:
+	//	  Can be a cleanup function.
+	//    Iris provides a cleanup function that will check for old entries and remove them.
+	// 	  You can customize it, e.g. check every 1 minute
+	// 	  if a client's last visit was 5 minutes ago ("old" entry)
+	//    and remove it from the memory.
+	rateLimiter := rate.Limit(1, 5, rate.PurgeEvery(time.Minute, 5*time.Minute))
+	app.Use(rateLimiter)
+
+	// Routes.
+	app.Get("/", index)
+	app.Get("/other", other)
+
+	return app
+}
+
+func index(ctx iris.Context) {
+	ctx.HTML("<h1>Index Page</h1>")
+}
+
+func other(ctx iris.Context) {
+	ctx.HTML("<h1>Other Page</h1>")
+}