Could not connect to (ws://slackarchive:8080/ws): %!(EXTRA string=websocket: bad handshake)

Everything is built and "running" however I am getting this error:

Could not connect to (ws://slackarchive:8080/ws): %!(EXTRA string=websocket: bad handshake)

And the page is blank, docs are a little light on setup and usage unless I missed something. Anyone have any suggestions? Thanks!

Start by reproducing the reported blank page and the websocket connection to ws://slackarchive:8080/ws using the setup described in the repository. Trace the handshake failure and verify the service configuration and endpoint; done means the page loads and the websocket connects without the reported error.

Written by the indexing model from the issue text.