race fails with negative wait group

In Fix data race with lookup paths (!822 - merged) we introduced a new test TestResolveLookupPathsConcurrentNetRequests that does some concurrent requests using sync.WaitGroup. The order in which we call the goroutine and the wg.Add(1) matters in this case because there is a chance the goroutine will finish faster than adding a delta to the wait group as seen in https://gitlab.com/gitlab-org/gitlab-pages/-/jobs/2769712947.

Job #2769712947 failed for 3bc6bfea: