autopool: 自动伸缩池，指定最小和最大连接，按需增加
workerpool: 工人令牌池，指定工人数和队列，池创建就已初始化工人数
Usage:
import (
"fmt"
"github.com/xEasy/pool/workerpool"
)
pool := workerpool.NewPool(WORKER_COUNT, JOB_QUEUE_LEGTH)
func helloWorld(w string) {
fmt.Print("hello", w)
}
pool.WaitCount(1)
pool.Enqueue(helloWorld, "world")
pool.WaitAll()
# release workpool
pool.Release()