nginx service commands not working any more if auto_ssl:init()

We have an openresty 1.11.2.2 on Ubuntu 12.04 LTS and/or Ubuntu 14.04, and we're having issues with the service start/stop commands since we started using lua-resty-auto-ssl.

I have been able to narrow it down to a single line in the configuration file.
Once the line `auto_ssl:init()` in nginx.conf is commented out of nginx.conf, everything works. (i.e. all normal nginx/openresty functionality)

Once the line `auto_ssl:init()` is active, nginx can be started _once_ using `service nginx start` or `start nginx`, but when a stop is attempted (`service nginx stop` or `stop nginx`)
nginx does stop, but the stop command never returns, and from that moment on, the start and stop commands do not work any more, until a reboot. No nginx processes are left running.

nginx can still be started by issuing the `nginx` command, and stopped using `nginx -s stop`...

openresty is self-compiled, lua-resty-auto-ssl 0.10.5 is installed using luarocks.

Do you have some pointers on this?

Start with the nginx.conf line containing auto_ssl:init() and reproduce the behavior on the reported OpenResty and Ubuntu versions using service nginx start/stop, start/stop, and nginx -s stop. Compare the service-command behavior with auto_ssl:init() commented out, then identify the cause and verify that nginx stops cleanly and subsequent start and stop commands return normally.

Written by the indexing model from the issue text.