WaitGroup

Go WaitGroup Reuse Requires Completed Wait Boundaries

A sync.WaitGroup can be reused after a wait phase completes, but a new independent task set cannot begin while calls to Wait from the prior phase are still active. The boundary is the return of every earlier Wait, not merely the instant at which the internal task counter reaches zero. This constraint matters when one WaitGroup instance is retained across batches, epochs, request waves, or repeated coordination cycles. Reuse is supported, but phases must not overlap at the zero-to-positive counter transition.