koa-ws-2.js

function *noop(){}

Ws.prototype.onConnection = function *(client) {

    try {
        var ctx = this.web.koa_app.createContext(client.upgradeReq, {statusCode: null});
        yield this.web.session_.bind(ctx)(noop);

        var sessionId = ctx.sessionId;
        this.logger.info("WebSocket.onConnection", sessionId);
        ...
    }
    ...
}
...

Ws.prototype.init = function *() {
    var wss = new WebSocketServer({server: this.koa.httpsServer});
    wss.on('connection', co.wrap(this.onConnection).bind(this))
}