bump go to 1.21

[Jefftree]

/assign @alexzielenski

Since k/k is already on 1.21.

Integration go.sum changes were from running a go mod tidy in that directory.

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: Jefftree

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• OWNERS [Jefftree]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[alexzielenski]

It looks like k8s 1.26 is still in support and uses Go 1.19.

Is it possible that in the future we would need to bump the k8s dep on kube-openapi for a bugfix? If thats the case I think making this change would require the older versions of k8s use go1.21 also

[Jefftree]

That's a good point, although we'd most likely cut a new branch and add a specific commit off of the version of the kube-openapi dependency from the k8s version? Fast forwarding to the latest version is usually undesired since we don't provide backwards compatibility guarantees and could include unwanted features when we're targeting bug fixes. I haven't seen any cases of a bug-fix backport but if you feel that's an important use case I'm okay with delaying this PR.

[alexzielenski]

Yes I see now we have a separate branch for releases that needed backports. Didn't realize that was our process for this repo.

/lgtm