public async Task EnterAsync_WhenCompleted_LockIsAcquired()
{
await _mutex.EnterAsync(Key, CancellationToken.None);
using (var cancellationTokenSource = new CancellationTokenSource(TimeSpan.FromSeconds(3)))
{
await Assert.ThrowsAsync <OperationCanceledException>(() => _mutex.EnterAsync(Key, cancellationTokenSource.Token));
}
await _mutex.ExitAsync(Key);
}