> I'm curious how?

    if rand.Intn(2) == 0 {
        select {
           case: <-chan2_whichItreatTheSameAsChan3 // a higher priority
           case: 0xFF ->chan3_whichItreatTheSameAsChan2
        }
    } else {
        select {
           case: 0xFF ->chan3_whichItreatTheSameAsChan2 // a higher priority
           case: <-chan2_whichItreatTheSameAsChan3
        }
    }