并发读取file io.Reader

        var sm sync.Map
	var wg sync.WaitGroup
	length := len(ckNode.master)
	var w = make([]io.Writer, length, length)
	var pr = make([]*io.PipeReader, length, length)
	c := make(chan struct{}, length)
	for i := 0; i < length; i++ {
		wg.Add(1)
		go func(index int) {
			pr[index], w[index] = io.Pipe()
			c <- struct{}{}
			cid, err = ckNode.ipfs.Add(pr[index], shell.Pin(true))
			sm.Store(cid, err)
			wg.Done()
		}(i)
	}
	// 写入通道全部启动才开始copy
	for {
		if len(c) == length {
			break
		}
	}
	mw := io.MultiWriter(w...) // 向mw统一写入
	_, err = io.Copy(mw, file)
	if err != nil {
		return "", err
	}
	for i := 0; i < length; i++ {
		if pw, ok := w[i].(*io.PipeWriter); ok {
			pw.CloseWithError(err)
		}
	}
	wg.Wait()
	sm.Range(func(key, value interface{}) bool {
		if value != nil {
			err = value.(error)
			return false
		}
		if cid != "" && cid != key.(string) {
			err = errors.New("cid不一致出现错误！")
			return false
		}
		cid = key.(string)
		return true
	})