public Containerizer setExecutorService(@Nullable ExecutorService executorService) {
    this.executorService = executorService;
    return this;
  }
Sets the {@link ExecutorService} Jib executes on. Jib, by default, uses {@link
Executors#newCachedThreadPool}.

@param executorService the {@link ExecutorService}
@return this
jib-core/src/main/java/com/google/cloud/tools/jib/api/Containerizer.java