Go debug code from Rob Pike. Updated with a Println that works (thanks guelfey from #go-nuts)

debug.go

const debug debugging = true // or flip to false

type debugging bool

func (d debugging) Println(args ...interface{}) {
    if d {
        log.Println(append([]interface{}{"DEBUG:"}, args...)...)
    }
}
func (d debugging) Printf(format string, args ...interface{}) {
    if d {
        log.Printf("DEBUG:" + format, args...)
    }
}

My understanding is that this is from https://github.com/golang/glog and relies on the compiler inlining these nop functions when the const debug is set to false (https://groups.google.com/forum/#!topic/golang-nuts/TzuGe1rcQ4Y).

I'm personally using this pattern only as a temporary solution for in-line debugging calls in application code, as the compiler output still has effects from the debug code (nop calls and code memory use). This 'if debug' pattern relies on a compilation feature (inlining functions/methods with no effects, and removing the nop inline) that has to be implemented correctly for each platform to work as expected.