Support for docker secrets in ENV

[Sector14]

Would it be possible to add additional ENV options to read from a file in order to support docker secrets?

Describe the solution you'd like
Rather than setting S3_ACCESS_KEY_ID=mysecretkey

I'd like to instead set a _FILE version e.g S3_ACCESS_KEY_ID_FILE=/run/secrets/mydockersecret

Reading that file will then provide you with "mysecretkey". Having _FILE support for the S3_ACCESS_KEY_ID and S3_SECRET_KEY would be useful, as well as any future ENV items that may be expected to hold secrets.

Describe alternatives you've considered
Mounting an entire env file as a docker secret is probably a viable workaround but it's a bit hacky.

The _FILE option of env vars is how other projects have provided support for docker secrets and seems to be the "norm". For example MySQL. See "MYSQL_PASSWORD_FILE" at the following link https://docs.docker.com/engine/swarm/secrets/#advanced-example-use-secrets-with-a-wordpress-service

[dekobon]

Are you using AWS S3 or another S3 compatible object store?

[Sector14]

Using minio (and backblaze) both S3 compatible.