I wrote a systemd timer for lego

[ysc3839]

https://gist.github.com/ysc3839/6e967c4541f585107eebb6bb777a7935

Place lego.service and lego.service in /etc/systemd/system.
Place config in /var/lib/lego and nginx-example.com.sh in /var/lib/lego/scripts.
You should modify config and nginx-example.com.sh.
Finally execute sudo systemctl enable lego.timer.

Lego's files are stored in /var/lib/lego. You need to create this directory and use lego ... run to create acme account.

I'm using DNS challenge and didn't test HTTP challenge. Please tell me if it works.