How to create channel routes on Lumen

I previously created a chat application using Laravel Framework. You can check in my github (https://github.com/fendiseptiawan0709/laravel-chat). On Laravel Framework there is a route that handles channel registration at routes/channel.php. However when I try to create an application in Lumen, I do not find the files routes/channel.php, I only find routes/web.php. How can I register a route channel in Lumen while there are no routes/channels.php files in my application? Please help me to solve this problem. thank you