You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: thread_pool.rb
    path of file: ./repos/stackneveroverflow/vendor/bundle/ruby/2.3.0/gems/puma-3.9.1/lib/puma
    
    the code of the file until where you have to start completion: require 'thread'

module Puma
  # A simpl
    
      def start!
        @running = true

        @thread = Thread.new do
          while @running
            @pool.reap
            sleep @timeout
          end
        end