let resp = await fetch('https://<url>', {
            headers: {
                Upgrade: 'websocket',
            },
        });

        let ws = resp.webSocket;
        if (!ws) {
            throw new Error("server didn't accept WebSocket");
        }

        ws.accept();

        let resp = await fetch('https://<url>', {
            headers: {
                Upgrade: 'websocket',
            },
        });

        let ws = resp.webSocket;
        if (!ws) {
            throw new Error("server didn't accept WebSocket");
        }

        ws.accept();