Variable expansion supported?

[mecampbellsoup]

It doesn't seem like the following syntax/contents of a .env file is currently supported, is that correct or am I missing a flag perhaps?

GOOGLE_OAUTH_CLIENT_ID=${GOOGLE_OAUTH_CLIENT_ID:-oauth-client-id}

The goal is to mirror what docker compose does, i.e. you can set an env var to (1) the value from your host, or (2) some fallback specified via normal shell variable expansion syntax:

web:
	environment:
		- DEBUG=${DEBUG:-false}