Using go's websocket library would also be viable.

For the receiving end, go can use http handlers for websockets. So when a message from any websocket is received the handler will be spawn and process it (just as any http request). Preferably dispatch it to a big central channel.

Keeping separate channels for each websocket seems overkill to me. Go has maps. Create a map with all the websocket connections and maybe smaller maps for each chat room, then set n workers to listen to the central channel and dispatch messages directly to each room member.