This fixes a couple of references to loop variables in parallel tests
and deferred functions. When running a parallel test (calling
`t.Parallel()`) combined with the table-driven pattern, it's necessary
to copy the test case loop variable, otherwise only the last test case
is exercised. This is documented in the `testing` package:
https://pkg.go.dev/testing#hdr-Subtests_and_Sub_benchmarks
`defer` statements that invoke a closure should also not reference a
loop variable directly as the referenced value will change in each
iteration of the loop.
Issues were automatically found with the `loopvarcapture` linter.
