cannot find package "math/bits"

If I try to update from Gitlab 10.8.x with go 1.8.3 (which is the only supported version regarding the upgrade guide) the make command fails with

root@prod /srv/git/gitaly # sudo -u git -H make
go install -ldflags '-X gitlab.com/gitlab-org/gitaly/internal/version.version=0.104.0 -X gitlab.com/gitlab-org/gitaly/internal/version.buildtime=20180614.205546' gitlab.com/gitlab-org/gitaly/cmd/gitaly gitlab.com/gitlab-org/gitaly/cmd/gitaly-ssh
_build/src/gitlab.com/gitlab-org/gitaly/vendor/golang.org/x/crypto/ssh/cipher.go:19:2: cannot find package "math/bits" in any of:
	/srv/git/gitaly/_build/src/gitlab.com/gitlab-org/gitaly/vendor/math/bits (vendor tree)
	/usr/local/go/src/math/bits (from $GOROOT)
	/srv/git/gitaly/_build/src/math/bits (from $GOPATH)
Makefile:55: recipe for target 'build' failed
make: *** [build] Error 1

It seems that math/bits is only included in go 1.9 and upgrading to go 1.9.1 resolves the issue.