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

Former-commit-id: ed635ee95de7160cde11eaabc0c1dcb0e460a620

_examples/routing/versioning/main.go

@@ -0,0 +1,73 @@
+package main
+
+import (
+	"github.com/kataras/iris/v12"
+	"github.com/kataras/iris/v12/versioning"
+)
+
+func main() {
+	app := iris.New()
+
+	examplePerRoute(app)
+	examplePerParty(app)
+
+	// Read the README.md before any action.
+	app.Listen(":8080")
+}
+
+// How to test:
+// Open Postman
+// GET: localhost:8080/api/cats
+// Headers[1] = Accept-Version: "1" and repeat with
+// Headers[1] = Accept-Version: "2.5"
+// or even "Accept": "application/json; version=2.5"
+func examplePerRoute(app *iris.Application) {
+	app.Get("/api/cats", versioning.NewMatcher(versioning.Map{
+		"1":                 catsVersionExactly1Handler,
+		">= 2, < 3":         catsV2Handler,
+		versioning.NotFound: versioning.NotFoundHandler,
+	}))
+}
+
+// How to test:
+// Open Postman
+// GET: localhost:8080/api/users
+// Headers[1] = Accept-Version: "1.9.9" and repeat with
+// Headers[1] = Accept-Version: "2.5"
+//
+// POST: localhost:8080/api/users/new
+// Headers[1] = Accept-Version: "1.8.3"
+//
+// POST: localhost:8080/api/users
+// Headers[1] = Accept-Version: "2"
+func examplePerParty(app *iris.Application) {
+	usersAPI := app.Party("/api/users")
+
+	// version 1.
+	usersAPIV1 := versioning.NewGroup(">= 1, < 2")
+	usersAPIV1.Get("/", func(ctx iris.Context) {
+		ctx.Writef("v1 resource: /api/users handler")
+	})
+	usersAPIV1.Post("/new", func(ctx iris.Context) {
+		ctx.Writef("v1 resource: /api/users/new post handler")
+	})
+
+	// version 2.
+	usersAPIV2 := versioning.NewGroup(">= 2, < 3")
+	usersAPIV2.Get("/", func(ctx iris.Context) {
+		ctx.Writef("v2 resource: /api/users handler")
+	})
+	usersAPIV2.Post("/", func(ctx iris.Context) {
+		ctx.Writef("v2 resource: /api/users post handler")
+	})
+
+	versioning.RegisterGroups(usersAPI, versioning.NotFoundHandler, usersAPIV1, usersAPIV2)
+}
+
+func catsVersionExactly1Handler(ctx iris.Context) {
+	ctx.Writef("v1 exactly resource: /api/cats handler")
+}
+
+func catsV2Handler(ctx iris.Context) {
+	ctx.Writef("v2 resource: /api/cats handler")
+}