go/neo: Switch benchmarkGetObject to xsync.WorkGroup

go/neo/neo_test.go

@@ -445,7 +445,7 @@ func benchmarkGetObject(b *testing.B, Mnet, Snet, Cnet xnet.Networker, benchit f
 	zback := xfs1back("../zodb/storage/fs1/testdata/1.fs")
 
 	ctx, cancel := context.WithCancel(context.Background())
-	wg, ctx := errgroup.WithContext(ctx)
+	wg := xsync.NewWorkGroup(ctx)
 	defer wg.Wait()
 	defer cancel()
 
@@ -462,7 +462,7 @@ func benchmarkGetObject(b *testing.B, Mnet, Snet, Cnet xnet.Networker, benchit f
 	traceMasterStartReady_Attach(tracer.pg, tracer.traceMasterStartReady)
 	tracing.Unlock()
 
-	wg.Go(func() error {
+	wg.Go(func(ctx context.Context) error {
 		return M.Run(ctx)
 	})
 
@@ -483,7 +483,7 @@ func benchmarkGetObject(b *testing.B, Mnet, Snet, Cnet xnet.Networker, benchit f
 	S := tNewStorage("abc1", Maddr, "", Snet, zback)
 	C := NewClient("abc1", Maddr, Cnet)
 
-	wg.Go(func() error {
+	wg.Go(func(ctx context.Context) error {
 		return S.Run(ctx)
 	})