Set and pass environment variable from Fastlane to calling bash script

Question

I am wanting to set an environment variable in Fastlane, and pass it back to a calling Bash script.

Just as a simple example, I run this Bash script:

#!/bin/sh

fastlane beta
echo $DELIVER_USER

Somewhere in my lane code I have:

sh(command: 'export DELIVER_USER=joe')

But the echo in the calling script does not show "joe", it doesn't show anything. Is there a way that I can do this? Or some other way to be able to pass a value from Fastlane back to the calling Bash script?