Multi-threaded features needed for Server

[b3liever]

If you're looking for synchronization primitives this 
[module](https://github.com/planetis-m/nim-100days/blob/master/multithread/thrsync.nim)
 I writing might be useful. It depends on an unreleased stdlib 
[patch](https://gist.github.com/xflywind/bf90bb478b4f5c7f062717d64cf557bd) by 
@xflywind. Eventually I would like to commit it to fusion.