Set stderr and stdout explicitly

[kamilsk]

Related to: #1869

Motivation: the patch uses stdout implicitly and affects testability.

Tested:

$ go run ./cmd/golangci-lint/ version 2>/dev/null
golangci-lint has version (devel) built from (unknown, mod sum: "") on (unknown)
$ go run ./cmd/golangci-lint/ version 1>/dev/null

[kamilsk]

I think that only main function should decide what input/output it uses. For example: https://github.com/octomation/go-tool/blob/271d0b52b43c560e24c2e66615a2d1c49347a1a3/main.go#L42-L43

It will require a bit more editing, but I can do it if needed.

[ldez]

What is the problem that solves this PR? 🤔

[kamilsk]

It solves the original problem #1868 but uses an explicit approach instead of implicit.

[kamilsk]

I suggest to restore the original code (revert https://github.com/golangci/golangci-lint/pull/1869/files) and configure stderr/stdout explicitly.

[ldez]

For me, #1869 fixes #1868, what is the value to do it differently? 🤔

[kamilsk]

After #1869 the only possible way to test it is integration test, because you need to check os.Stdout. The pr fixes that and you can write unit test instead of integration test to check output, just provide buffer as stdout/stderr.