# File lib/rufus/scheduler.rb, line 134
    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