Jeff, Digital Ocean mirrors haven’t made 18.04 ready for do-release-update yet. I tried reinstalling docker using:
wget -qO- https://get.docker.com/ | sh
… and then rebooting, I don’t know why the service is failing to start after doing so, though.
Maybe I didn’t remove it properly first, any pointers on how to remove and reinstall docker properly?
Right now docker --version says: Docker version 18.06.0-ce, build 0ffa825