If there is an error, would it possible to still print the command? It makes it easier to debug generation issues.

Ya, that makes sense to me. The error would be any error that occurs after this line, right?

I could handle it by adding something like this:

} else {
    log.SetPrefix(fmt.Sprintf("command %s", arg))
}

but that might make for some strange log messages.

Another option would be moving everything below this out into a new function which returns errors instead of log.Fatal() and adding the extra text here in the if err != nil.

WDYT?

Looking at it again, I guess it's really only the protoc.run() error that needs to be handled, so I added a log.Println(err) to that if block.