改版了下书上的计算目录下所有总目录的文件大小，执行后小目录的可以跑出结果，但是根盘就不行，报错，求大佬指导
```
import (
"fmt"
"os"
"path/filepath"
"sync"
"time"
)
var done = make(chan struct{})
func cancelled() bool {
select {
case <-done:
return true
default:
return false
}
}
func main() {
// Determine the initial directories.
roots := os.Args[1:]
if len(roots) == 0 {
roots = []string{"."}
}
go func() {
os.Stdin.Read(make([]byte, 1)) // read a single byte
close(done)
}()
fileSizes := make(chan map[string]int64)
var n sync.WaitGroup
for _, root := range roots {
n.Add(1)
go walkDir(root, &n, fileSizes)
}
go func() {
n.Wait()
close(fileSizes)
}()
tick := time.Tick(500 * time.Millisecond)
var nbytes = make(map[string]int64)
loop:
for {
select {
case <-done:
// Drain fileSizes to allow existing goroutines to finish.
for range fileSizes {
// Do nothing.
}
return
case size, ok := <-fileSizes:
if !ok {
break loop // fileSizes was closed
}
for k, v := range size {
nbytes[k] += v
}
case <-tick:
//printDiskUsage(nfiles, nbytes)
}
}
for k, v := range nbytes {
if v > 10*1e9 {
printDiskUsage(k, v) // final totals
}
}
}
func printDiskUsage(nfiles string, nbytes int64) {
fmt.Printf("【%s】:【%.1f GB】\n", nfiles, float64(nbytes)/1e9)
}
func walkDir(dir string, n *sync.WaitGroup, fileSizes chan<- map[string]int64) {
dirsSize := make(map[string]int64) //需要有个缓冲，不然并发报错
defer n.Done()
if cancelled() {
return
}
for _, entry := range dirents(dir) {
if entry.IsDir() {
n.Add(1)
subdir := filepath.Join(dir, entry.Name())
go walkDir(subdir, n, fileSizes)
} else {
dirsSize[dir] += entry.Size()
}
fileSizes <- dirsSize
}
}
var sema = make(chan struct{}, 20) // concurrency-limiting counting semaphore
func dirents(dir string) []os.FileInfo {
select {
case sema <- struct{}{}: // acquire token
case <-done:
return nil // cancelled
}
defer func() { <-sema }() // release token
f, err := os.Open(dir)
if err != nil {
fmt.Fprintf(os.Stderr, "du: %v\n", err)
return nil
}
defer f.Close()
entries, err := f.Readdir(0) // 0 => no limit; read all entries
if err != nil {
fmt.Fprintf(os.Stderr, "du: %v\n", err)
// Don't return: Readdir may return partial results.
}
return entries
}
```
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