I'm using Kubernetes, and mounted a volume on /etc, which contains Caddyfile. DNS wasn't working as expected, and it's because I overwrote /etc/resolv.conf.
It's a minor thing but perhaps suggesting it be mounted on a more specific folder will make it less like that others fall into the same trap? Perhaps /etc/caddy.
I resolved mine by specifing the command to run to include -conf /path/to/my/Caddyfile