Previously, nonce values were fetched from Directory URL. RFC8555 and some recent drafts provide specific URL to fetch new nonce values from. This CL makes the client always use new nonce URL when available and fall back to the previous behavior otherwise. Updates golang/go#21081 Change-Id: I6442004b01d46aa015c193ca4c80daa712b78790 Reviewed-on: https://go-review.googlesource.com/c/crypto/+/191603 Run-TryBot: Alex Vaghin <ddos@google.com> TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>