How to connect client to server?

[japangermany1998]

First, I created a server

    app := iris.New()

    var ws = neffos.New(websocket.DefaultGorillaUpgrader, neffos.Namespaces{
        .....
    })

    crs := cors.New(cors.Options{
        AllowedOrigins:   []string{"*"},
        AllowCredentials: true,
    })
    app.Get("/echo",crs, websocket.Handler(ws))

    log.Fatal(app.Listen(":8000"))

In javascript, I create client connect to server.

async function example() {
        try {
            const conn = await neffos.dial("ws://localhost:8000/echo", {
                v1: {
                    chat: function (nsConn, msg) {
                        window.alert(msg.Body);
                    }
                }
            });

            const nsConn = await conn.connect("v1");
            nsConn.emit("chat", "Greetings!");

        } catch (err) {
            console.log(err);
        }
    }
    example();

Then I run javascript then connect failed.

But if i create client using golang, it worked since I can use gorilla.DefaultDialer. How can I use the same for Javascript?