SSL Certificates generation when reconfigure system

[c4droid]

Hi, I'm using guix deploy to manage my cloud server from NixOS with
deploy-rs, I deployed some web application in server and using nginx as
reverse proxy. After setup certbot-service-type and deploy, the nginx
not started, I found not certificates in /etc/letsencrypt. In NixOS,
NixOS will generates ssl certificates when system switching, Guix System
seems not implement is feature, have something workaround for it?
I tried generate certificates manually, the certbot will block
certificate generation when 80 port is used, actually the 80 port not in
use and no web server running in background.