Show a progress bar

progress.go

package main

import (
	"fmt"
	"time"
)

const total = 5 * time.Second

type process struct {
	step  time.Duration
	total time.Duration
}

type processes map[int]*process

func main() {
	var currentProcesses = make(processes)
	var progressBar = make(chan int, len(currentProcesses))

	currentProcesses.AddProcess(1, total)
	currentProcesses.AddProcess(2, total)
	currentProcesses.AddProcess(3, total)

	go writeOutput(progressBar, currentProcesses)

	progressBar <- 1
	progressBar <- 2
	progressBar <- 3

	go updateProgressBar(progressBar, currentProcesses, 1, 1000*time.Millisecond)
	go updateProgressBar(progressBar, currentProcesses, 2, 500*time.Millisecond)
	go updateProgressBar(progressBar, currentProcesses, 3, 100*time.Millisecond)

	time.Sleep(10 * time.Second)
}

func (p processes) AddProcess(id int, total time.Duration) {
	p[id] = &process{total: total}
}

func (p *process) UpdateProcess(step time.Duration) {
	p.step = step
}

func updateProgressBar(progressBar chan<- int, currentProcesses processes, id int, step time.Duration) {
	steps := int(currentProcesses[id].total) / int(step)

	for i := 0; i < steps; i++ {
		time.Sleep(step)
		currentProcesses[id].UpdateProcess(time.Duration((i+1) * int(step)))
		progressBar <- id
	}
}

func writeOutput(progressBar <-chan int, currentProcesses processes) {
    for {
        x := <-progressBar
        s := ""
        for _, process := range currentProcesses {
            s += outputProgress(x, int(process.step), int(process.total))
        }

        fmt.Printf("\033[0;0H")
        fmt.Print(s)
    }
}

func outputProgress(id int, step, total int) string {
    current := percent(step, total)
    s := fmt.Sprintf("Doing Task %d [", id)

	for i := 0; i < current; i++ {
		s += "="
	}

	for i := current; i < 100; i++ {
		s += " "
	}

	s += fmt.Sprintf("] %d%%\r\n", current)

	return s
}

func percent(step, total int) int {
	return int(float32(step) / float32(total) * 100)
}