实际上 MaxQueue 没起到作用，发生问题后任务压在这个相对轻量一些的 goroutine 上而已

for{
select{
case job:= <-JobQueue:
// a job request has been received
fmt.Println("Store a job into jobChannel")
go func(job Job){
//try to obtain a worker job channel that is available.
//this will block until a worker is idle
jobChannel := <- d.WorkerPool
//dispatch the job to the worker job channel
jobChannel <- job
}(job)
}
}