As far is I know docker opens huge security backdoor by opening its ports to external so I added:
...
garie-pagespeed-insights:
image: "garie/pagespeed-insights"
ports:
- 127.0.0.1:3002:3000
...
That restricts to localhost and you can easily redirect all requests and several ports with nginx:
#13
Unfortunately I have build this outside of docker but I think this idea is maybe worth considering to run this programmatically as docker nginx module.