Fix lint/go errors

[kentakozuka]

What happened:

A Command make lint/go returns many errors.

What you expected to happen:

How to reproduce it:

Environment:

• piped version:
• control-plane version:
• Others:

[karamaru-alpha]

I'd like to take up this issue :)
I plan to resolve all lint errors and Integrate golangci-lint into GitHub Actions.

[khanhtc1202]

Todo:

• Confirm make lint/go return no error
• Update CI to use make lint/go probably

[dgannon991]

I've just had a quick run locally, and there are quite a few issues still present (17 stylecheck, 4 unparam, 4 ineffassign, 8 gocritic) so I'll hop onto this one next, as I'd like to get a bit more familiar with the go code :)
Just a quick check on this one actually, is pkg/app/pipedv1 still in use? Just because there also seems to be a pkg/app/piped? Cheers!