Mastodon with nginx-gen and letsencrypt

I recently setup a mastodon instance, on my docker host, using a combination of nginx-gen, nginx, and docker-letsencrypt-nginx-proxy-companion

nginx-gen allows addition of custom nginx config to each virtual host, based on the name of the virtual host, as defined by the VIRTUAL_HOST variable.

All the instructions I found online for mastodon and nginx included proxypass to /api/v1/streaming, to the streaming container on port 4000, but in the case of nginx-proxy, you get a virtual host per-container.

In order to forward just the /api/v1/streaming URL, I added the following to vhost.d/

location /api/v1/streaming {