in lib/pool.dart [261:271]
void _onResourceReleased() {
_resetTimer();
if (_requestedResources.isNotEmpty) {
var pending = _requestedResources.removeFirst();
pending.complete(PoolResource._(this));
} else {
_allocatedResources--;
if (isClosed && _allocatedResources == 0) _closeGroup!.close();
}
}