panic: sync: negative WaitGroup counter

[jackleibest]

using the following codes:
var wg sync.WaitGroup
_, err := download.Boot().
URL(args.url).
Listener(func(event *download.Event) {
if event.Key == download.EventKeyProgress {
printProgress(event.Task, "downloading...")
}
if event.Key == download.EventKeyFinally {
var title string
if event.Err != nil {
title = "fail"
} else {
title = "complete"
}
printProgress(event.Task, title)
fmt.Println()
if event.Err != nil {
fmt.Printf("reason: %s", event.Err.Error())
} else {
fmt.Printf("saving path: %s", *args.dir)
}
wg.Done()
}
}).
Create(&base.Options{
Path: *args.dir,
Extra: http.OptsExtra{Connections: *args.connections},
})
if err != nil {
panic(err)
}
wg.Add(1)
wg.Wait()

and got the panic: sync: negative WaitGroup counter error:
panic: sync: negative WaitGroup counter

goroutine 29685 [running]:
sync.(*WaitGroup).Add(0x1b28c40?, 0x4?)
/usr/local/go/src/sync/waitgroup.go:62 +0xe5
sync.(*WaitGroup).Done(...)
/usr/local/go/src/sync/waitgroup.go:87
media.downloadFile.func1(0xc00021f590)
/root/apps/netstream/gstream/media/downloader.go:51 +0x257
github.com/GopeedLab/gopeed/pkg/download.(*Downloader).emit(0xc000136660, {0x126257b, 0x7}, 0xc00083c780, {0xc00089ef58?, 0x10fe500?, 0xc00083ca00?})
/root/apps/netstream/gstream/thirdparty/gopeed/pkg/download/downloader.go:410 +0xe5
github.com/GopeedLab/gopeed/pkg/download.(*Downloader).watch(0xc000136660, 0xc00083c780)
/root/apps/netstream/gstream/thirdparty/gopeed/pkg/download/downloader.go:483 +0x134
github.com/GopeedLab/gopeed/pkg/download.(*Downloader).Create.func2()
/root/apps/netstream/gstream/thirdparty/gopeed/pkg/download/downloader.go:285 +0x90
created by github.com/GopeedLab/gopeed/pkg/download.(*Downloader).Create
/root/apps/netstream/gstream/thirdparty/gopeed/pkg/download/downloader.go:279 +0x6f8

[monkeyWie]

Fix in #110.

[jackleibest]

actually, I had put the wg.Add(1) in front of the beginning, like this, still got the promblem. it happens occasionally, especially in parallel downloading.

url:="https://xxxx.com/xxx.mp4"
connections :=8
var wg sync.WaitGroup
wg.Add(1)
_, err := download.Boot().URL(url).Listener(func(event *download.Event) {
	if event.Key == download.EventKeyProgress {
		//printProgress(event.Task, "downloading...", callbackProgress)
	}
	if event.Key == download.EventKeyFinally {
		//printProgress(event.Task, title, callbackProgress)
		fmt.Println()
		if event.Err != nil {
			log.Error("download failed: ", event.Err.Error())
		} else {
			log.Info("download success: ", url)
		}
		wg.Done()
	}
}).Create(&base.Options{
	Extra: http.OptsExtra{Connections: connections},
	DisableRename: true,
})
if err != nil {
	log.Error(err)
}
wg.Wait()

[monkeyWie]

Can u provide gopeed version?

[jackleibest]

using the latest repo.

[monkeyWie]

There is no DisableRename option in the latest version. Did you add it yourself?

[jackleibest]

yeah, becuase I wanna custom the save file name, so i disable the automatic rename, so sure it will not trigger the panic: sync: negative WaitGroup counter

[monkeyWie]

I have tested your code and was unable to reproduce the issue. This exception is only triggered when calling wg.Add(1) after calling wg.Done(), but the code seem fine.