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

Former-commit-id: ed635ee95de7160cde11eaabc0c1dcb0e460a620

_examples/routing/subdomains/single/main.go

@@ -0,0 +1,44 @@
+// Package main register static subdomains, simple as parties, check ./hosts if you use windows
+package main
+
+import (
+	"github.com/kataras/iris/v12"
+)
+
+func main() {
+	app := iris.New()
+
+	// Subdomain method is just another Party.
+	admin := app.Subdomain("admin")
+	{
+		// admin.mydomain.com
+		admin.Get("/", func(c iris.Context) {
+			c.Writef("INDEX FROM admin.mydomain.com")
+		})
+		// admin.mydomain.com/hey
+		admin.Get("/hey", func(c iris.Context) {
+			c.Writef("HEY FROM admin.mydomain.com/hey")
+		})
+		// admin.mydomain.com/hey2
+		admin.Get("/hey2", func(c iris.Context) {
+			c.Writef("HEY SECOND FROM admin.mydomain.com/hey")
+		})
+	}
+
+	// mydomain.com
+	app.Get("/", func(c iris.Context) {
+		c.Writef("INDEX FROM no-subdomain hey")
+	})
+
+	// mydomain.com/hey
+	app.Get("/hey", func(c iris.Context) {
+		c.Writef("HEY FROM no-subdomain hey")
+	})
+
+	// http://admin.mydomain.com
+	// http://admin.mydomain.com/hey
+	// http://admin.mydomain.com/hey2
+	// http://mydomain.com
+	// http://mydomain.com/hey
+	app.Listen("mydomain.com:80") // for beginners: look ../hosts file
+}