[pinum]

Instead of shutting down completely, why not this:

For goo.gl links that were created by google, continue redirecting them as normal. For others, show a warning page explaining to the user that the link wasn't created (or vouched for) by google. If they press an "agree" button, still don't show a clickable link, but instead show it as plain text to be copied.

[gkoberger]

Yeah, this is sorta what's already happening. They stopped new links years ago, and are only removing "inactive" links now.