When writing request headers, use `header(name, value)` to set the only occurrence of `name` to `value`. If there are existing values, they will be removed before the new value is added. Use `addHeader(name, value)` to add a header without removing the headers already present.

    queue.cancelActiveTask = false
    queue.activeTask = null
    busyQueues.remove(queue)

    if (delayNanos != -1L && !cancelActiveTask && !queue.shutdown) {
      queue.scheduleAndDecide(task, delayNanos, recurrence = true)
    }

    if (queue.futureTasks.isNotEmpty()) {
      readyQueues.add(queue)

      // If the task crashed, start another thread to run the next task.
      if (!completedNormally) {