server.go

package main

import (
	"fmt"
	"net/http"

	"github.com/gorilla/websocket"
)

func echo(w http.ResponseWriter, r *http.Request) {
	upgrader := websocket.Upgrader{}
	conn, _ := upgrader.Upgrade(w, r, nil)
	defer conn.Close()

	for {
		mt, message, _ := conn.ReadMessage()

		fmt.Printf("recv: %s\n", message)

		_ = conn.WriteMessage(mt, message)
	}
}

func main() {
	http.HandleFunc("/", echo)
	http.ListenAndServe(":8080", nil)
}