cli/ci: iox_test.go:108: not the error we expected <nil>

[bassosimone]

Describe the bug

The CI fails intermittently like this:

--- FAIL: TestCopyContextWithCancelledContext (0.00s)
Error:     iox_test.go:108: not the error we expected <nil>
FAIL
coverage: 100.0% of statements

See https://github.com/ooni/probe-cli/pull/445/checks?check_run_id=3381591044

To Reproduce
Run the CI multiple times per day, you should eventually see the failure.

Expected behavior
The test is not failing.

Screenshots
N/A

System information (please complete the following information):
GitHub Actions.

Additional context
I suppose the test works because of some race condition that does not always happen. If there is a timeout inside the test, then we should most likely increase it, so that the test works more often.

[bassosimone]

It turns out I've already fixed this issue in ooni/probe-cli#484.