The Perm function return 0 or 1 or 2 or 3. 4 is not returned,
so that changed the argument to 5.
Change-Id: Ic980c71a9f29f522bdeef4fce70a6c2dd136d791
Reviewed-on: https://go-review.googlesource.com/c/go/+/209777 Reviewed-by: Ian Lance Taylor <iant@golang.org>