Change minimal Go version to 1.21 and removed unnecessary test

[edmocosta]

• Changed minimal go version to 1.21 (stable version), so other libraries does not need to bump their Go versions to use it.
• Considering this library is not using (and probably won't use in the future) Goroutines, we can safety remove the package_test Goroutines leakage checks and avoid adding unneeded external decencies to the library.

[jsvd]

There is no reason given in the PR or the commit for the go version downgrade and removal of the test, can we add that to the commit message?

[edmocosta]

There is no reason given in the PR or the commit for the go version downgrade and removal of the test, can we add that to the commit message?

Hey @jsvd, I've added it on the PR description! thanks for reviewing :)

[jsvd]

Overall LGTM, I noticed you bumped .go-version again, maybe we could also bump versions in .golangci.yml so the library is tested with the most recent golang, even if it supports an older one.

[edmocosta]

Overall LGTM, I noticed you bumped .go-version again, maybe we could also bump versions in .golangci.yml so the library is tested with the most recent golang, even if it supports an older one.

I've adapted the .golangci.yml from another Elastic project, but it seems those go: ... versions on the linters have no effect, it should be on the run section instead. When it's empty, it defaults to the go.mod version and/or GOVERSION env var, which I think is the optimal behaviour for the linters. It also had a few invalid/deprecate settings that I fixed on the last commit.