* @param terminationTimeout how long to wait for the executor to finish before terminating the
   *     JVM
   * @param timeUnit unit of time for the time parameter
   * @return an unmodifiable version of the input which will not hang the JVM
   */
  @J2ktIncompatible
  @GwtIncompatible // TODO
  @SuppressWarnings("GoodTime") // should accept a java.time.Duration
  public static ExecutorService getExitingExecutorService(