add a simple docker example

Former-commit-id: cacfa3ad903ce542ce455cb2298c40639c645d3c

_examples/docker/main.go

@@ -0,0 +1,26 @@
+package main
+
+import (
+	"flag"
+
+	"github.com/kataras/iris/v12"
+)
+
+var addr = flag.String("addr", ":8080", "host:port to listen on")
+
+// $ docker-compose up
+func main() {
+	flag.Parse()
+
+	app := iris.New()
+
+	app.Get("/", func(ctx iris.Context) {
+		ctx.HTML("<strong>Hello World!</strong>")
+	})
+
+	app.Get("/api/values/{id:uint}", func(ctx iris.Context) {
+		ctx.Writef("id: %d", ctx.Params().GetUintDefault("id", 0))
+	})
+
+	app.Run(iris.Addr(*addr))
+}