To start caddy server using your own Caddyfile :
docker run --rm -p 443:443 -p 80:80 -v /path/to/config/file/:/conf tilkal-docker/caddy -conf /conf/Caddyfile
or
docker run --rm -p 443:443 -p 80:80 -v /path/to/config/file/Caddyfile:/opt/bin/Caddyfile tilkal-docker/caddy