Because we had the same issue I wrote a plugin for Caddy to use Consul’s KV (wich itself is a clustered too) as TLS storage backend. Please have a look here: GitHub - pteich/caddy-tlsconsul: 🔒 Consul K/V storage for Caddy Web Server / Certmagic TLS data
I also maintain a Docker image for a recent Caddy build with included Consul TLS plugin here:
https://hub.docker.com/r/pteich/caddy-tlsconsul/
We use this configuration and Docker image in production for many months now without any problem.