func main() {
        err := rpio.Open()
        if err != nil {
                os.Exit(1)
        }
        defer rpio.Close()

        pin := rpio.Pin(7)
        pin.Mode(rpio.Pwm)
        pin.Freq(60*60)
        pin.DutyCycle(0, 60)
        // the LED will be blinking at 60Hz
        // (source frequency divided by cycle length => 60*60/60 = 2000)
}