use SendContext to ensure no goroutine leaks

Author: easwars

xds/internal/xdsclient/tests/ads_stream_ack_nack_test.go

@@ -246,7 +246,7 @@ func (s) TestADS_ACK_NACK_InvalidFirstResponse(t *testing.T) {
 			return nil
 		},
 		OnStreamResponse: func(_ context.Context, _ int64, _ *v3discoverypb.DiscoveryRequest, resp *v3discoverypb.DiscoveryResponse) {
-			streamResponseCh.Send(resp)
+			streamResponseCh.SendContext(ctx, resp)
 		},
 	})
 
@@ -351,7 +351,7 @@ func (s) TestADS_ACK_NACK_ResourceIsNotRequestedAnymore(t *testing.T) {
 			return nil
 		},
 		OnStreamResponse: func(_ context.Context, _ int64, _ *v3discoverypb.DiscoveryRequest, resp *v3discoverypb.DiscoveryResponse) {
-			streamResponseCh.Send(resp)
+			streamResponseCh.SendContext(ctx, resp)
 		},
 	})