In playing with service workers, I set up a self-signed SSL certificate for my local development environment. I used instructions from debian.org. It was very simple, since I didn’t need the security involved with a real operating site. Creating the certs took a single command:
openssl req -new -x509 -days 365 -nodes -out /path/to/server/config/certs/sitename.pem -keyout /path/to/server/config/certs/sitename.key
You then just need to set things up in the server configuration (Apache in my case). mod_ssl must be installed and enabled, which looks something like: