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

Former-commit-id: ed635ee95de7160cde11eaabc0c1dcb0e460a620

_examples/routing/subdomains/wildcard/hosts

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+# Copyright (c) 1993-2009 Microsoft Corp.
+#
+# This is a sample HOSTS file used by Microsoft TCP/IP for Windows.
+#
+# This file contains the mappings of IP addresses to host names. Each
+# entry should be kept on an individual line. The IP address should
+# be placed in the first column followed by the corresponding host name.
+# The IP address and the host name should be separated by at least one
+# space.
+#
+# Additionally, comments (such as these) may be inserted on individual
+# lines or following the machine name denoted by a '#' symbol.
+#
+# For example:
+#
+#      102.54.94.97     rhino.acme.com          # source server
+#       38.25.63.10     x.acme.com              # x client host
+
+# localhost name resolution is handled within DNS itself.
+127.0.0.1       localhost
+::1             localhost
+#-iris-For development machine, you have to configure your dns also for online, search google how to do it if you don't know
+127.0.0.1		mydomain.com
+127.0.0.1		username1.mydomain.com
+127.0.0.1		username2.mydomain.com
+127.0.0.1		username3.mydomain.com
+127.0.0.1		username4.mydomain.com
+127.0.0.1		username5.mydomain.com
+
+#-END iris-

_examples/routing/subdomains/wildcard/main.go

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+// Package main an example on how to catch dynamic subdomains - wildcard.
+// On the first example we learnt how to create routes for static subdomains, subdomains you know that you will have.
+// Here we will see an example how to catch unknown subdomains, dynamic subdomains, like username.mydomain.com:8080.
+package main
+
+import (
+	"github.com/kataras/iris/v12"
+)
+
+// register a dynamic-wildcard subdomain to your server machine(dns/...) first, check ./hosts if you use windows.
+// run this file and try to redirect: http://username1.mydomain.com:8080/ , http://username2.mydomain.com:8080/ , http://username1.mydomain.com/something, http://username1.mydomain.com/something/sadsadsa
+
+func main() {
+	app := iris.New()
+
+	/* Keep note that you can use both type of subdomains (named and wildcard(*.) )
+	   admin.mydomain.com,  and for other the Party(*.) but this is not this example's purpose
+
+	admin := app.Party("admin.")
+	{
+		// admin.mydomain.com
+		admin.Get("/", func(ctx iris.Context) {
+			ctx.Writef("INDEX FROM admin.mydomain.com")
+		})
+		// admin.mydomain.com/hey
+		admin.Get("/hey", func(ctx iris.Context) {
+			ctx.Writef("HEY FROM admin.mydomain.com/hey")
+		})
+		// admin.mydomain.com/hey2
+		admin.Get("/hey2", func(ctx iris.Context) {
+			ctx.Writef("HEY SECOND FROM admin.mydomain.com/hey")
+		})
+	}*/
+
+	// no order, you can register subdomains at the end also.
+	dynamicSubdomains := app.Party("*.")
+	{
+		dynamicSubdomains.Get("/", dynamicSubdomainHandler)
+
+		dynamicSubdomains.Get("/something", dynamicSubdomainHandler)
+
+		dynamicSubdomains.Get("/something/{paramfirst}", dynamicSubdomainHandlerWithParam)
+	}
+
+	app.Get("/", func(ctx iris.Context) {
+		ctx.Writef("Hello from mydomain.com path: %s", ctx.Path())
+	})
+
+	app.Get("/hello", func(ctx iris.Context) {
+		ctx.Writef("Hello from mydomain.com path: %s", ctx.Path())
+	})
+
+	// http://mydomain.com:8080
+	// http://username1.mydomain.com:8080
+	// http://username2.mydomain.com:8080/something
+	// http://username3.mydomain.com:8080/something/yourname
+	app.Listen("mydomain.com:8080") // for beginners: look ../hosts file
+}
+
+func dynamicSubdomainHandler(ctx iris.Context) {
+	username := ctx.Subdomain()
+	ctx.Writef("Hello from dynamic subdomain path: %s, here you can handle the route for dynamic subdomains, handle the user: %s", ctx.Path(), username)
+	// if  http://username4.mydomain.com:8080/ prints:
+	// Hello from dynamic subdomain path: /, here you can handle the route for dynamic subdomains, handle the user: username4
+}
+
+func dynamicSubdomainHandlerWithParam(ctx iris.Context) {
+	username := ctx.Subdomain()
+	ctx.Writef("Hello from dynamic subdomain path: %s, here you can handle the route for dynamic subdomains, handle the user: %s", ctx.Path(), username)
+	ctx.Writef("The paramfirst is: %s", ctx.Params().Get("paramfirst"))
+}