chore: continue porting code and adding test coverage

src/StevesBot.Worker/Threading/AsyncLock.cs

@@ -0,0 +1,24 @@
+namespace StevesBot.Worker.Threading;
+
+internal sealed class AsyncLock : IAsyncLock
+{
+  private readonly SemaphoreSlim _semaphore = new(1, 1);
+  private bool _disposed;
+
+  public async Task<IDisposable> LockAsync(CancellationToken cancellationToken = default)
+  {
+    await _semaphore.WaitAsync(cancellationToken);
+    return new LockReleaser(_semaphore);
+  }
+
+  public void Dispose()
+  {
+    if (_disposed)
+    {
+      return;
+    }
+
+    _semaphore.Dispose();
+    _disposed = true;
+  }
+}