code: def add
        raise 'Block must be given to start()' unless block_given?
        latch = Concurrent::CountDownLatch.new(1)
        thread = Thread.start do
          Thread.current.name = @title
          VerboseThread.new(@log).run do
            latch.count_down
            yield
          end
        end
        latch.wait
        Thread.current.thread_variable_set(
          :kids,
          (Thread.current.thread_variable_get(:kids) || []) + [thread]
        )
        @threads << thread
      end
docs: Add a new thread