This docker container is based on googles kms golang examples. https://github.com/GoogleCloudPlatform/golang-samples/blob/master/kms/crypter/crypter.go
Usage:
Mount a volume that contains the location of a service.json file
Then inject an environmental variable that tells the tool where to find those credentials
using the GOOGLE_APPLICATION_CREDENTIALS
docker run convrrt/google-kms {encrypt, decrypt} {keyring} {cryptokey} {infile} {outfile}