make sure Abort is holding untill inner goroutine finishes

bar.go

@@ -268,15 +268,19 @@ func (b *Bar) SetPriority(priority int) {
 // if bar is already in complete state. If drop is true bar will be
 // removed as well.
 func (b *Bar) Abort(drop bool) {
+	done := make(chan struct{})
 	select {
 	case b.operateState <- func(s *bState) {
 		if s.completed == true {
+			close(done)
 			return
 		}
-		if drop {
-			go b.container.dropBar(b)
-		} else {
-			go func() {
+		// container must be run during lifetime of this inner goroutine
+		// we control this by done channel declared above
+		go func() {
+			if drop {
+				b.container.dropBar(b)
+			} else {
 				var uncompleted int
 				b.container.traverseBars(func(bar *Bar) bool {
 					if b != bar && !bar.Completed() {
@@ -286,16 +290,15 @@ func (b *Bar) Abort(drop bool) {
 					return true
 				})
 				if uncompleted == 0 {
-					select {
-					case b.container.refreshCh <- time.Now():
-					case <-b.container.done:
-					}
+					b.container.refreshCh <- time.Now()
 				}
-			}()
-		}
+			}
+			close(done) // release hold of Abort
+		}()
 		b.cancel()
 	}:
-		<-b.done
+		// guarantee: container is alive during lifetime of this hold
+		<-done
 	case <-b.done:
 	}
 }