The most simple threadsafe progress bar in go

hershey.go

package hershey

import (
	"fmt"
	"math"
	"strings"
	"sync"
	"time"
)

type Bar struct {
	mut     sync.Mutex
	percent int
	current int
	total   int
}

func New(total int) *Bar {
	return &Bar{total: total, current: 0, percent: 0}
}

func (bar *Bar) Done(n int) {
	bar.mut.Lock()
	defer bar.mut.Unlock()
	bar.current += n
	bar.percent = int(math.Min(100, (float64(bar.current)/float64(bar.total))*100))
	fmt.Printf("\r[%-50s]%3d%% %8d/%d", strings.Repeat("=", bar.percent/2), bar.percent, bar.current, bar.total)
}

func (bar *Bar) Finish() {
	bar.current = bar.total
	fmt.Println()
}