internal var shutdown = false

  /** This queue's currently-executing task, or null if none is currently executing. */
  internal var activeTask: Task? = null

  /** Scheduled tasks ordered by [Task.nextExecuteNanoTime]. */
  internal val futureTasks = mutableListOf<Task>()

  /** True if the [activeTask] should be canceled when it completes. */
  internal var cancelActiveTask = false

  /**