cmd/go: add -tests to list of vet checks run by "go test"

[kybin]

What version of Go are you using (go version)?

go 1.15.8

What did you do?

I resturctured my test TestXXX as an example ExampleXXX. But forgot to remove the argument.

What did you expect to see?

ExampleXXX(t *testing.T) is wrong signature for an example (has *testing.T as an argument),
so it should raise error on go test.

What did you see instead?

It didn't run. Made me assumes the test has successfully finished.

[D1CED]

Is at least correctly reported on the playground https://play.golang.org/p/dj_FUdOxN1j

[ianlancetaylor]

The problem is reported by go vet.

[kybin]

@D1CED Ah, I thought it isn't relevant to playground, my guess was wrong.

@ianlancetaylor I keep forget about go vet, thanks. Doesn't go test do basic vetting? I feel that I read it somewhere...

[ianlancetaylor]

Yes, go test runs go vet by default. But it only runs it with a limited set of vet tests, ones that are considered to be very reliable when it comes to showing problems. Perhaps we should add this check to that list.

I'll change this issue into a proposal to do that.

[kybin]

Great, thank you.