I want to add env variables to new instances

I want all my deployments to have access to postgres, thus I'm creating a plugin which sets up a new user with access to a new database (on a postgres server in a different container). I want to expose the database access with an env variable, just like heroku does. To me it looks like release is the best place to put this hook.
Added X-Forwarded-For to pass client IP to backend
Build image from Dockerfile instead of curl S3
Merge pull request #145 from msumpter/patch-2

Added X-Forwarded-For to pass client IP to backend
Redeploy apps on reboot, fixes #82
Merge pull request #178 from asm89/redeploy

Redeploy apps on reboot, fixes #82
Merge pull request #134 from phaza/patch-1

I want to add env variables to new instances
Merge pull request #168 from Kloadut/docker-build

Build image from Dockerfile instead of curling S3
Merge branch 'master' of https://github.com/progrium/dokku