Package fallback has no API; its only purpose is to automatically call x509.SetFallbackRoots with a set of fallback roots. That API was added in Go 1.20, hence the go1.20 build constraint in fallback.go. Add that constraint to bundle.go too, so that it fails to build rather than quietly being a no-op in Go 1.19. Also simplify Write(fmt.Sprintf()) into fmt.Fprintf while here. Add a temporary workaround for go.dev/issue/52287. It has no effect on the public API in this module. For golang/go#57792. For golang/go#52287. Change-Id: I1fe13f7d54b07b0b031e8bae685cffd7a8160165 Reviewed-on: https://go-review.googlesource.com/c/crypto/+/505578 Auto-Submit: Dmitri Shuralyov <dmitshur@golang.org> TryBot-Result: Gopher Robot <gobot@golang.org> Reviewed-by: Dmitri Shuralyov <dmitshur@google.com> Reviewed-by: Roland Shoemaker <roland@golang.org> Run-TryBot: Dmitri Shuralyov <dmitshur@golang.org>