class Rufus::Scheduler

def shutdown(opt=nil)
  @started_at = nil
  #jobs.each { |j| j.unschedule }
    # provokes https://github.com/jmettraux/rufus-scheduler/issue/98
  @jobs.array.each { |j| j.unschedule }
  @work_queue.clear
  if opt == :wait
    join_all_work_threads
  elsif opt == :kill
    kill_all_work_threads
  end
  unlock
end