Decrypt with gpg from inside a docker container
Depending on your base image (used by your container), you would need to add to your Dockerfile
(or to make one, starting with FROM <the image used by your container>) with:
RUN apt-get update && apt-get install gnupg(as in this docker-vault-init Dockerfile)
Then check out "Adding GPG key inside docker container causes “no valid OpenPGP data found”".
This could be needed:
RUN apt-get install -y ca-certificates wget