Traverses a directoty tree with muptiple threads

DirectoryTraverser.cs

var checkPath = new DirectoryInfo(startPath);
//HACK Paths should be an IEnummerable
var f = new FoundDir(checkPath.FullName, FoundDir.RootDir, 0);
ConcurrentQueue<FoundDir> directories = new();
directories.Enqueue(f);
Task[] parallelTasks = { Task.Run(() => DirScan(3)), Task.Run(() => DirScan(2)), Task.Run(() => DirScan(1)) };
Task.WhenAll(parallelTasks).Wait();
async Task DirScan(long instance)
{
    while (instance > directories.Count)
    {   // Wait until enough items in the queue, otherwise the Task would finish immediately
        Thread.Yield();
    }   //HACK Here has to be cancelled, if the queue never gets long enough
    Console.WriteLine($"{instance:D2}: instance started");
    while (directories.TryDequeue(out var directoryItem))
    {
        Console.WriteLine($"{instance:D2}: {directoryItem.Outline} {directoryItem.FullPath}");
        try
        {
            var index = 0;
            foreach (string subDir in Directory.GetDirectories(directoryItem.FullPath))
            {
                directories.Enqueue(new FoundDir(subDir, directoryItem, index++));
                Thread.Yield();
            }
        }
        catch (Exception ex)
        {
            Console.Error.WriteLine(ex);
        }
        //HACK here has to be waited: Does the last item has subdirectories?
    }
    Console.WriteLine($"{instance:D2}: instance finished");
}
/// <summary>A <see cref="System.IO.FileSystemInfo"/> stores the full path twice: OriginalPath and FullPath.
/// We want to store only the name, the parent folder (and a hash value?). </summary>
public class FoundDir
{
    public FoundDir(string path, FoundDir parent, long index)
    { // ...
    }
}