This example isn't particularly good code. If you've got "lots of code" that names a bunch of variables (e.g. using ':=') that are never referenced AND you have a good reason not to do so (which I doubt: given this context it looks like an incomplete test), then predeclare these 'excess' variables:

   func TestWhatever(t *testing.T) {
        var resp3, resp4, fooBefore, subFoo, bar2, barNew, zap2 theirType

        // ...lots of code
   }

Alternatively, use '_' where they are being defined:

   // instead of
   resp2, err := doit()

   // use
   _, err := doit()

If, and given this context it's likely, you're checking these errors with asserts, then either change the name of the error variable, predeclare the err name (`var err error`), or split it into multiple tests instead of one giant spaghetti super test.

That said, in a code review, at a minimum, I would probably ask that these variables be checked for nil/default which would completely eliminate this problem.

The good news is if you use Nix or Guix it’s relatively easy to hack your local build of the compiler to demote the unused variables hard error to just a warning.

All of this could've been prevented if Go just had two ways to compile. Debug and release.

The go devs decided against this since they didn't want to build a highly optimizing (read: slow) compiler, but that is missing the point of developer ergonomics.