Bump Go build version to 1.17
Bump Go build version to 1.17

Motivation: make darwin_arm64 artifact available as part of the release

The *Installation instructions* already refers to Go v1.17 and above, and
the README.md states:

  *We recommend always using the newest stable release of Go.*

Please note, that is not yet a working change set. It appears that a

  go mod tidy

is needed to make the build step work.

google/go-jsonnet,google/go-jsonnet,google/go-jsonnet,google/go-jsonnet,google/go-jsonnet