异步等待，代码永远不会执行

Im使用此方法提交对eventstore的更改，然后在eventstore更新后发布事件
我的问题是，代码永远不会到达aggregate.MarkChangesAsCommitted方法和下一个await。

    public async Task CommitChanges()
    {
        foreach (var aggregate in _trackedAggregates.Values)
        {
            var newEvents = aggregate.GetChanges();
            await _eventStorage.Save(aggregate.Id, newEvents);
            aggregate.MarkChangesAsCommitted();
            await _eventPublisher.Publish(newEvents);
        }
    }

事件存储

    public Task Save(Guid aId, IEnumerable<IDomainEvent> events)
    {
        return new Task(() =>
        {
            using (var stream = _store.OpenStream(aId))
            {
                foreach (var domainEvent in events)
                {
                    stream.Add(new EventMessage
                    {
                        Body = domainEvent
                    });
                }
                stream.CommitChanges(Guid.NewGuid());
            }
        });
    }