The current version of the docs doesn't list anything for nginx - it mentions a page in the FAQ that supposedly has a config, but that leads to a 404:

https://coder.com/docs/tutorials/faqs#how-do-i-configure-nginx-as-the-reverse-proxy-in-front-of-coder
https://coder.com/docs/admin/setup/web-server/nginx

Normally I'd just use a standard nginx configuration for this, but it seems like it needs more than that, since a websocket connection is complaining about needing an upgrade:
WebSocket protocol violation: handshake request must be at least HTTP/1.1: "HTTP/1.0" unable to accept:failed to accept WebSocket connection: WebSocket protocol violation: handshake request must be at least HTTP/1.1: "HTTP/1.0"