add customizable server name

ms.go

@@ -17,6 +17,10 @@ func main() {
 	if os.Getenv("PORT") != "" {
 		port = os.Getenv("PORT")
 	}
+	serverName := "localhost"
+	if os.Getenv("SERVER_NAME") != "" {
+		serverName = os.Getenv("SERVER_NAME")
+	}
 
 	rand.Seed(time.Now().Unix())
 
@@ -26,8 +30,8 @@ func main() {
 
 	router.GET("/", func(c *gin.Context) {
 		c.HTML(http.StatusOK, "index.html", gin.H{
-			"websocket": "ws://localhost:" + port + "/ws",
-			"sse":       "http://localhost:" + port + "/sse",
+			"websocket": "ws://" + serverName + ":" + port + "/ws",
+			"sse":       "http://" + serverName + ":" + port + "/sse",
 		})
 	})
 	router.GET("/ws", websocketHandler(websocket.Upgrader{