fix(golangci-lint): Run linter on the directory

[gnuletik]

Fixes false positives from unused & typecheck linters.

For example:
mypackage/a.go has function myFunc()
mypackage/b.go use function myFunc()

threw a unused error in mypackage/a.go and a undef error in mypackage/b.go

This now checks the files in all directories instead of the current file/buffer

[bhcleek]

golangci-lint is only given the file to lint when linting on save. In that case, we only want to lint the file being saved.

[bhcleek]

I understand why you want to do this, though. Perhaps the right solution is to filter the errors coming back from golangci-lint on the filenames. That's relatively easy to do with the job support in vim-go...

[bhcleek]

Thank you for the PR. I'm going to merge this soon and extend it to support vim-go expected behavior.

[gnuletik]

@bhcleek Thanks for having a look !

Yes filtering the errors on the current filename seems totally appropriate.
If you know how this can be done, okay :) I'm farily new to vimscript.

Thanks !

[bhcleek]

Doing this as-is causes other problems, too. When not in GOPATH, golangci-lint run doesn't seem to report any problems when then argument it's given is a directory instead of a file.

[bhcleek]

I created golangci/golangci-lint#592 to demonstrate the problem that golangci-lint is having. Since the problem is limited to null modules, I'll likely merge this PR with some additional changes soon.