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

Former-commit-id: ed635ee95de7160cde11eaabc0c1dcb0e460a620

_examples/http-server/http3-quic/main.go

@@ -0,0 +1,29 @@
+package main
+
+import (
+	"github.com/kataras/iris/v12"
+
+	"github.com/lucas-clemente/quic-go/http3"
+)
+
+/*
+	$ go get -u github.com/lucas-clemente/quic-go/...
+	# or if you're using GO MODULES:
+	$ go get github.com/lucas-clemente/quic-go@master
+*/
+
+func main() {
+	app := iris.New()
+
+	app.Get("/", func(ctx iris.Context) {
+		ctx.Writef("Hello from Index")
+	})
+
+	// app.Configure(iris.WithOptimizations, or any other core config here)
+	// app.Build()
+	// http3.ListenAndServe(":443", "./localhost.cert", "./localhost.key", app)
+	// OR:
+	app.Run(iris.Raw(func() error {
+		return http3.ListenAndServe(":443", "./localhost.cert", "./localhost.key", app)
+	}))
+}