整理した

src/server/api/stream/channel.ts

@@ -1,8 +1,10 @@
 import * as websocket from 'websocket';
 import * as redis from 'redis';
+import { ParsedUrlQuery } from 'querystring';
 
 export default function(request: websocket.request, connection: websocket.connection, subscriber: redis.RedisClient): void {
-	const channel = request.resourceURL.query.channel;
+	const q = request.resourceURL.query as ParsedUrlQuery;
+	const channel = q.channel;
 
 	// Subscribe channel stream
 	subscriber.subscribe(`misskey:channel-stream:${channel}`);