Handling WebSocket Upgrade Request

[cloudwindy]

Hello, I'm using koa-better-http-proxy, and the following code to support websocket upgrade:

/**
 * Create a WebSocket server.
 * @param server Server
 */
createWebSocketServer(server: http.Server | https.Server | http2.Http2SecureServer) {
	server.on('upgrade', (req: http.IncomingMessage, sock: net.Socket, head: Buffer) => {
		server.emit('request', req, new UpgradableResponse(sock, head));
	});
	const createContext = this.app.createContext;
	this.app.createContext = (req: http.IncomingMessage, res: http.ServerResponse | UpgradableResponse) => {
		const ctx: Koa.Context = createContext.call(this.app, req, res);
		if (res instanceof UpgradableResponse) {
			ctx.ws = true;
			ctx.upgrade = () => res.upgrade(req);
		}
		return ctx;
	};
}

The UpgradeableReponse provides a upgrade method which returns a ws.WebSocket instance. Then the method is copied in the overridden createContext to be made accessible in ctx. ctx.ws is also set to true to indicate this connection is upgradable.

However, I can't figure out how to implement this in koa-better-http-proxy and act like nginx's proxy_pass.