internal/cp/copy.go: defer file.Close() confusion

[dalechyn]

Hey. I am a little confused in what is going on with deferring files closing in internal/cp/copy.go.

if err := out.Close(); err != nil {
    return err
}

Isn't it an extra call to out.Close() since we have defer out.Close()?

If it is not, and It's just me missing something with Go defer call handling, why there is no error check for defer in.Close()?

[stapelberg]

The deferred call is for avoiding resource leaks (we don’t care if it fails), the non-deferred call is for checking whether flushing the file to disk fails.

This is intentional :)