[BUGFIX] Fixes to expChan reachability during mass data deletion (#140)

Signed-off-by: kpango <kpango@vdaas.org>

example/main.go

@@ -146,10 +146,22 @@ func main() {
 		return true
 	})
 
+	runtime.GC()
+	gch := gache.New[int64]().EnableExpiredHook().
+		SetExpiredHook(func(ctx context.Context, key string) {
+			glg.Debugf("key=%v expired", key)
+		}).
+		StartExpired(context.Background(), time.Second*10)
+	for i := 0; i < 10000; i++ {
+		gch.SetWithExpire("sample-"+strconv.Itoa(i), int64(i), time.Second*5)
+	}
+	time.Sleep(time.Second * 20)
+	glg.Debugf("length: %d", gch.Len())
+
 	runtime.GC()
 	gcs := gache.New[string]()
 	maxCnt := 10000000
-	digitLen :=  len(strconv.Itoa(maxCnt))
+	digitLen := len(strconv.Itoa(maxCnt))
 	for i := 0; i < maxCnt; i++ {
 		if i%1000 == 0 {
 			// runtime.ReadMemStats(&m)

gache.go

@@ -144,20 +144,22 @@ func (g *gache[V]) SetExpiredHook(f func(context.Context, string)) Gache[V] {
 // StartExpired starts delete expired value daemon
 func (g *gache[V]) StartExpired(ctx context.Context, dur time.Duration) Gache[V] {
 	go func() {
-		tick := time.NewTicker(dur)
 		var cancel context.CancelFunc
 		ctx, cancel = context.WithCancel(ctx)
 		g.cancel.Store(&cancel)
+		tick := time.NewTicker(dur)
 		for {
 			select {
 			case <-ctx.Done():
 				tick.Stop()
 				return
-			case <-tick.C:
-				g.DeleteExpired(ctx)
-				runtime.Gosched()
 			case key := <-g.expChan:
 				go g.expFunc(ctx, key)
+			case <-tick.C:
+				go func() {
+					g.DeleteExpired(ctx)
+					runtime.Gosched()
+				}()
 			}
 		}
 	}()