Environment Variable for JDBC Connect URL

Not sure if what I'm looking to do is missing a small piece of syntax or is unsupported. Say I have a database connection where the connect string property is

jdbc:mysql://localhost:3306/test

If I have that stored to an environment variable $MY_VAR (which I can correctly print in Ignition context and get the same jdbc:mysql://localhost:3306/test returned), what would I have to put in the DB connect string information to get it to expand the environment variable and process the value as the connection? Right now everything I have tried simply processes as a string literal of whatever variation of $MY_VAR and tells me there is no appropriate driver type

No such functionality. Sorry.

The closest you can get in a supported fashion is to use a locally-defined domain name in the database URL, where it is resolved from /etc/hosts or a similar local resource.

Got it, thank you