Go Exercise: Create a 5 minute Timer that displays the current remaining time in terminal

timer.go

package main

import (
	"fmt"
	"sync/atomic"
	"time"
)

type SecondsCounter struct {
	count int32
}

func pad_number(number int32) string {
	if number < 10 {
		return fmt.Sprintf("0%d", number)
	}
	return fmt.Sprintf("%d", number)
}

func format_timer(seconds int32) string {
	return fmt.Sprintf("%s:%s", pad_number((seconds%3600)/60), pad_number((seconds%3600)%60))
}

func print_timer(seconds *SecondsCounter) {
	fmt.Println(format_timer(atomic.LoadInt32(&seconds.count)))
}

func add_to_timer(seconds *SecondsCounter, amount int32) {
	atomic.AddInt32(&seconds.count, amount)
}

func main() {
	ticker := time.NewTicker(1000 * time.Millisecond)
	done := make(chan bool)

	seconds := new(SecondsCounter)

	add_to_timer(seconds, 300)
	print_timer(seconds)

	go func() {
		for {
			select {
			case <-done:
				return
			case <-ticker.C:
				add_to_timer(seconds, -1)
				print_timer(seconds)
			}
		}
	}()

	time.Sleep(5 * time.Minute)
	ticker.Stop()
	done <- true
	fmt.Println("Timer Done")
}