tests: set GOTOOLCHAIN var for report validation

[MadhavJivrajani]

Set GOTOOLCHAIN directive in order to successfully run tests
from root. Else, go will try and download a family of releases
(of the form 1.x), which are not published binaries.

Ref: #17733 (comment)

[serathius]

Looks like I didn't keep up with latest Golang features. Don't know toolchain feature enough to make long term decision yet, however short term would be good to be consistent. The choice is either .go-version file with #17733 (comment), or migrate to toolchain.

I think until we decide to remove .go-version file, I would prefer it to be source of go version in the project.

[ahrtr]

Agreed to use .go-version as the single source of truth of the go&toolchain version. Then I think we may want to update the build script to use the .go-version as the toolchain version as well.

[MadhavJivrajani]

Hey all, getting back to this PR

@jmhbnz that's a good point. I've made the change that uses the .go-version file instead to set the GOTOOLCHAIN env var.

Also, as next steps, we could do what Kubernetes does: https://github.com/kubernetes/community/blob/aea3ba11fc4dee0ae21f20c7412c732b79c666eb/contributors/devel/development.md#building-kubernetes-using-a-specific-version-of-go

Maybe have a way of setting the GOTOOLCHAIN env var as a prereq to running tests in general.

[ahrtr]

Please feel free to merge this PR if any maintainer wants.

But we need to revisit the go version management. Please read #17857

[serathius]

Please feel free to merge this PR if any maintainer wants.

But we need to revisit the go version management. Please read #17857

Right, want to merge as the makefile command apparently doesn't work for @MadhavJivrajani ref #17733 (comment)