It mentions time.Format3339Nano, which isn’t defined. The
underlying code uses time.RFC3339Nano.

Updates golang/go#24542

Change-Id: Ia34ae8b66427139d9005f902c2eb60aac4bfa8c6
Reviewed-on: https://go-review.googlesource.com/102607Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>