Turn off screen after timeout, script for Ubuntu.

black.go

package main

import (
	"os/exec"
	"time"
)

const work = 40
const rest = 5

func main() {

	for {
		time.Sleep(work * time.Minute)
		for end := time.Now().Add(rest * time.Minute); time.Now().Before(end); {
			exec.Command("xset", "dpms", "force", "off").Run()
			time.Sleep(time.Second)
		}
		exec.Command("xset", "dpms", "force", "on").Run()
	}

}