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

Former-commit-id: ed635ee95de7160cde11eaabc0c1dcb0e460a620

_examples/auth/recaptcha/main.go

@@ -0,0 +1,40 @@
+package main
+
+import (
+	"github.com/kataras/iris/v12"
+	"github.com/kataras/iris/v12/middleware/recaptcha"
+)
+
+// keys should be obtained by https://www.google.com/recaptcha
+const (
+	recaptchaPublic = ""
+	recaptchaSecret = ""
+)
+
+func showRecaptchaForm(ctx iris.Context, path string) {
+	ctx.HTML(recaptcha.GetFormHTML(recaptchaPublic, path))
+}
+
+func main() {
+	app := iris.New()
+
+	// On both Get and Post on this example, so you can easly
+	// use a single route to show a form and the main subject if recaptcha's validation result succeed.
+	app.HandleMany("GET POST", "/", func(ctx iris.Context) {
+		if ctx.Method() == iris.MethodGet {
+			showRecaptchaForm(ctx, "/")
+			return
+		}
+
+		result := recaptcha.SiteVerify(ctx, recaptchaSecret)
+		if !result.Success {
+			/* redirect here if u want or do nothing */
+			ctx.HTML("<b> failed please try again </b>")
+			return
+		}
+
+		ctx.Writef("succeed.")
+	})
+
+	app.Listen(":8080")
+}