If you want to create a new certificate, have a look at the end of this article.
In my case I already had a certificate which covered
I have a directory on my server called dev that I want to reference via dev.golightlyplus.com.
So to do that, I issued the following command
certbot -d golightlyplus.com,dev.golightlyplus.com,www.golightlyplus.com --expand
- re-include every domain name you want on that certificate again. I forgot www. the first time. No biggie, just re-run with all the domains you want.
- don’t forget to add --expand to the end
After reading around on the net a bit, I found this solution on this GitHub thread.