tests: fix Flaky TestMicroserviceTSOServer/TestConcurrentlyReset (#6396)

close #6385

Get a copy of now then call base.add, because now is shared by all goroutines and now.add() will add to itself which isn't atomic and multi-goroutine safe.

Signed-off-by: Bin Shi <binshi.bing@gmail.com>

tests/integrations/tso/server_test.go

@@ -154,7 +154,10 @@ func (suite *tsoServerTestSuite) TestConcurrentlyReset() {
 		go func() {
 			defer wg.Done()
 			for j := 0; j <= 100; j++ {
-				physical := now.Add(time.Duration(2*j)*time.Minute).UnixNano() / int64(time.Millisecond)
+				// Get a copy of now then call base.add, because now is shared by all goroutines
+				// and now.add() will add to itself which isn't atomic and multi-goroutine safe.
+				base := now
+				physical := base.Add(time.Duration(2*j)*time.Minute).UnixNano() / int64(time.Millisecond)
 				ts := uint64(physical << 18)
 				suite.resetTS(ts, false, false)
 			}