Asyncthread problem with -d:release on

#Problem: Errors with -d:release on, otherwise no problems.
#Problem is on windows(haven't tested on others) that it closes without giving any warning. So it just crashes.
#Nim version 0.11.2

import asyncdispatch
import rawsockets
import threadpool
import net

type
    ChannelServerWorker = ref object
        SockChan: TChannel[TAsyncFD]
        S: Server

    Server = ref object
        Workers: seq[ChannelServerWorker]
        Sockets: seq[TAsyncFD]
        Listener: Socket

proc Idle(csw: ChannelServerWorker) {.async.} =
    while true:
        await sleepAsync(100)

proc HandleSock(sock: TAsyncFD) {.async.} =
    while true:
        let data = await sock.recv(1023)
        if data != "":
            echo(data)
        else:
            break
    closeSocket(sock)

proc Run(csw: ChannelServerWorker) =
    csw.SockChan.open()
    asyncCheck csw.Idle()
    while true:
        let sockTuple = csw.SockChan.tryRecv()
        if sockTuple.dataAvailable:
            let sock = sockTuple.msg
            register(sock)
            asyncCheck sock.HandleSock()
        else:
            poll(1)

proc NewServer():Server =
    var server = Server()
    server.Workers = @[]
    server.Sockets = @[]
    server.Listener = newSocket()
    return server

proc Run(server: Server, numCores:int=3) =
    var threads = newSeq[TThread[ChannelServerWorker]](numCores)
    #Start the threads:
    for t in threads.mitems:
        var csw = ChannelServerWorker()
        csw.S = server
        server.Workers.add(csw)
        t.createThread Run, csw

    server.Listener.bindAddr(Port(5587), "127.0.0.1")
    server.Listener.listen()

    #Loop forever, accept new sock for every worker
    while true:
        for worker in server.Workers:
          var client: Socket = Socket()
          accept(server.Listener, client)
          client.getFd().setBlocking(false)
          worker.SockChan.send(client.getFd().TAsyncFD)


var server = NewServer()
server.Run(3)