Use toolchain to define desired Go version

[HeavyWombat]

Follow-up from: #6305 (comment)

Ref: https://go.dev/doc/modules/gomod-ref#go

Use toolchain to define the desired Go compiler version to be used.

Use go directive to show the minimum version it can still compile with.

Checklist

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Relates to #6305

[HeavyWombat]

I ran go mod tidy and go mod vendor, which led to changes in the vendor that surprised me to be honest.

[JorTurFer]

/run-e2e internal
Update: You can check the progress here

[JorTurFer]

I see the benefits of not limiting the minimum version but only suggesting it in case of 3rd parties using KEDA as dependency, but we also must ensure that the user version to build and ship KEDA is the desired one and (AFAIK), toolchain is more a suggestion than a requirement (not like the go directive which is mandatory).

Our current approach is based on generating updated build tools image so the toolchain available should be the same or above than the one in the go.mod. This point leads me to another question, how we can maintain the minimum version of the go directive? If we update a dependency that increases the minimum go version (like k8s deps), will the go directive updated automatically?

[wozniakjan]

If we update a dependency that increases the minimum go version (like k8s deps), will the go directive updated automatically?

I think so, both go and toolchain directives are updated with go get -u. As far as I can tell, go is updated based on the dependencies and toolchain is updated based on the available toolchain on the machine.

I ran go mod tidy and go mod vendor, which led to changes in the vendor that surprised me to be honest.

it's possible those are not related to the toolchain directive addition, the vendor is maintained best effort in a semi-automated fashion iirc

[wozniakjan]

lgtm

should we add a changelog entry? I think it's not necessary.

[JorTurFer]

/run-e2e internal
Update: You can check the progress here