C# AsyncLock based on SemaphoreSlim

AsyncLock.cs

public class AsyncLock
{
    private readonly SemaphoreSlim semaphore = new SemaphoreSlim(1, 1);
    private readonly Task<IDisposable> releaser;

    public AsyncLock()
    {
        releaser = Task.FromResult((IDisposable)new AsyncLockReleaser(this));
    }

    public Task<IDisposable> LockAsync(CancellationToken cancellationToken)
    {
        Task wait = semaphore.WaitAsync(cancellationToken);
        return wait.IsCompleted ?
            releaser :
            wait.ContinueWith(
                (_, state) => (IDisposable)state!,
                releaser.Result,
                CancellationToken.None,
                TaskContinuationOptions.ExecuteSynchronously,
                TaskScheduler.Default);
    }

    private sealed class AsyncLockReleaser : IDisposable
    {
        private readonly AsyncLock toRelease;

        internal AsyncLockReleaser(AsyncLock toRelease) {
            this.toRelease = toRelease;
        }

        public void Dispose()
        {
            toRelease.semaphore.Release();
        }
    }
}