Errgroup

Go errgroup SetLimit Blocks Submitters at the Concurrency Cap

errgroup.Group.SetLimit can block the goroutine that calls Group.Go. The limit is enforced before a new worker goroutine starts, so a full group applies backpressure at task submission rather than building an internal queue. That behavior matters when submission is part of another control path. A loop that appears to launch work asynchronously can itself stop at g.Go(...) until one active function returns. The limit sits on admission A zero-value errgroup.Group has no concurrency limit. After SetLimit(n), at most n functions started by Go are active at once. A negative limit restores unlimited admission, while a zero limit prevents every later Go call from starting a function.