spanner: increases timeout in TestIntegration_ReadOnlyTransaction.

Fixes #1890.

Change-Id: I07033fefc7c281ff93bf1b421697c801b6af8a8d
Reviewed-on: https://code-review.googlesource.com/c/gocloud/+/55871
Reviewed-by: Knut Olav Løite <koloite@gmail.com>
Reviewed-by: kokoro <noreply+kokoro@google.com>
diff --git a/spanner/integration_test.go b/spanner/integration_test.go
index 239d39b..3d0f5be 100644
--- a/spanner/integration_test.go
+++ b/spanner/integration_test.go
@@ -629,7 +629,7 @@
 func TestIntegration_ReadOnlyTransaction(t *testing.T) {
 	t.Parallel()
 
-	ctxTimeout := 30 * time.Second
+	ctxTimeout := 5 * time.Minute
 	ctx, cancel := context.WithTimeout(context.Background(), ctxTimeout)
 	defer cancel()
 	// Set up testing environment.