我想获取每个线程的返回值（比如是一个 hash），该怎么操作呢？
这样可以么？
thr = Thread.new { Thread.current[:return] = "some hash" }
thr.join
thr[:return] # some hash
轻量点的还可以用 queue，工作线程把结果放到 queue 里，收集的线程去取，没内容的话，收集的线程会 blocking。
http://ruby-doc.org/stdlib-2.0.0/libdoc/thread/rdoc/Queue.html
result = []
threads = []
5.times do |num|
threads << Thread.new{
result << {Thread.current.object_id.to_s => num}
}
end
threads.each {|thread| thread.join}
p result
输出
[{"69885727586360"=>0}, {"69885727586220"=>1}, {"69885727586080"=>2}, {"69885727585620"=>3}, {"69885727585480"=>4}]
