Add socket.io example

Former-commit-id: 895669c537db46f1694e8006418ea0509c60cb04

_examples/websocket/socketio/main.go

@@ -0,0 +1,54 @@
+// Package main runs a go-socket.io based websocket server.
+// An Iris compatible clone of: https://github.com/googollee/go-socket.io#example,
+// use of `iris.FromStd` to convert its handler.
+package main
+
+import (
+	"fmt"
+	"log"
+
+	socketio "github.com/googollee/go-socket.io"
+	"github.com/kataras/iris/v12"
+)
+
+func main() {
+	app := iris.New()
+	server, err := socketio.NewServer(nil)
+	if err != nil {
+		log.Fatal(err)
+	}
+	server.OnConnect("/", func(s socketio.Conn) error {
+		s.SetContext("")
+		fmt.Println("connected:", s.ID())
+		return nil
+	})
+	server.OnEvent("/", "notice", func(s socketio.Conn, msg string) {
+		fmt.Println("notice:", msg)
+		s.Emit("reply", "have "+msg)
+	})
+	server.OnEvent("/chat", "msg", func(s socketio.Conn, msg string) string {
+		s.SetContext(msg)
+		return "recv " + msg
+	})
+	server.OnEvent("/", "bye", func(s socketio.Conn) string {
+		last := s.Context().(string)
+		s.Emit("bye", last)
+		s.Close()
+		return last
+	})
+	server.OnError("/", func(s socketio.Conn, e error) {
+		fmt.Println("meet error:", e)
+	})
+	server.OnDisconnect("/", func(s socketio.Conn, reason string) {
+		fmt.Println("closed", reason)
+	})
+	go server.Serve()
+	defer server.Close()
+
+	app.HandleMany("GET POST", "/socket.io/{any:path}", iris.FromStd(server))
+	app.HandleDir("/", "./asset")
+	app.Run(iris.Addr(":8000"),
+		iris.WithoutPathCorrection,
+		iris.WithoutServerError(iris.ErrServerClosed),
+	)
+}