Go’s strong concurrency model makes it ideal for I/O-bound tasks, where real-time progress feedback is often needed. While simple carriage-return (\r) tricks suffice for basic single-bar use cases, they fall short in production-grade scenarios:

• Managing multiple concurrent progress bars requires precise synchronization and terminal state management.
• ANSI escape sequences behave inconsistently across platforms—especial in Windows PowerShell—leading to misaligned or corrupted output.
• Dynamic terminal resizing, mixed-width Unicode characters (e.g., CJK glyphs), and variable-length labels complicate line-length tracking and overwriting logic.
• Advanced UX needs—like hiding the cursor, disabling input during updates, or preserving layout across resize events—are unsupported by naive implementations.

Overview

progress is a Go library designed for robust, cross-platform, concurrent-safe progress visualization in terminal environments. It supports simultaneous rendering of heterogeneous progress indicators with full Unicode compatibility—including East Asian scripts—and provides fine-grained control over appearance, behavior, and lifecycle.

Key features include:

• Platform-agnostic ANSI handling via single-line-print foundation.
• Event-driven rendering (not timer-polling), minimizing I/O pressure and ensuring stability under high bar counts.
• Configurable bar styles: standard, inline, text-only, and animated loading indicators.
• Rich customization: spacing, width, color, float precision, visibility flags, and emoji support.
• Automatic terminal adaptation: dynamic width detection, cursor visibility control, and input blocking.

Installation

go get github.com/lianggaoqiang/progress

Basic Usage

package main

import (
	"github.com/lianggaoqiang/progress"
	"time"
)

func main() {
	p := progress.Start()
	bar := progress.NewBar()
	p.AddBar(bar)

	for i := 0; i <= 100; i++ {
		bar.Inc()
		time.Sleep(10 * time.Millisecond)
	}
}

This renders a default horizontal bar updating from 0% to 100%.

Custom Styling

Use Custom() to define visual elements:

b := progress.NewBar().Custom(progress.BarSetting{
	StartText:       "[",
	EndText:         "]",
	PassedText:      "-",
	FirstPassedText: ">",
	NotPassedText:   "=",
})

BarSetting fields include:

• LeftSpace, RightSpace: padding strings.
• Total: number of fill characters inside the bar.
• Hidden, HidePercent, UseFloat: display toggles and precision control.
• StartText, EndText: delimiters.
• PassedText, NotPassedText, FirstPassedText: fill glyphs.
• PercentColor: ANSI color index (e.g., progress.Green).

Colorization

Apply ANSI colors using helper functions:

b := progress.NewBar().Custom(progress.BarSetting{
	NotPassedText: progress.WhiteText("▇"),
	PassedText:    progress.ColorText("▇", progress.Green),
})

Supported color constants: Black, Red, Green, Yellow, Blue, Purple, Cyan, White.

Alternative Indicators

TextBar

For static status messages:

tb := progress.NewTextBar(progress.GreenText("Ready!"))
p.AddBar(tb)

LoadingBar

For indeterminate activity:

lb := progress.NewLoadingBar(
	300,
	"Loading",
	"Loading.",
	"Loading..",
	"Loading...",
)
lb.SetColor(progress.Red)
p.AddBar(lb)

The first argument is the frame interval in milliseconds. Subsequent strings rotate as frames. To reuse previous text, use - as shorthand (e.g., "-.", "-.", "-..."). For literal -, escape as -- or wrap as -(--).

LoadingBarSetting adds FixedWidth, which locks width to the longest frame.

Composing Multiple Bars

Bars render in insertion order, enabling complex layouts:

p := progress.Start()

b1 := progress.NewBar().Custom(progress.BarSetting{
	Total: 50, StartText: "[", EndText: "]",
	PassedText: "-", FirstPassedText: ">", NotPassedText: "=",
})

b2 := progress.NewBar().Custom(progress.BarSetting{
	UseFloat: true, Inline: true,
	StartText: "|", EndText: "|",
	FirstPassedText: ">", PassedText: "=", NotPassedText: " ",
})

b3 := progress.NewBar().Custom(progress.BarSetting{
	LeftSpace: 10, Total: 10,
	StartText: "|", EndText: "|",
	PassedText: "⚡", NotPassedText: "  ",
})

p.AddBar(b2)
p.AddBar(b3)
p.AddBar(b1)

for i := 0; i <= 100; i++ {
	b1.Inc()
	b2.Add(1.4)
	b3.Percent(float64(i))
	time.Sleep(40 * time.Millisecond)
}

Configuration Flags

Initialize with StartWithFlag() for advanced behavior:

• HideCursor: hides terminal cursor during rendering.
• DisableInput: blocks keyboard input while active.
• ResizeReactively: rechecks terminal width before each render.
• PercentOverflow: allows values >100%, disabling auto-stop.
• AutoStop: stops automatically when all bars reach 100% and loader are inactive.

Example:

p := progress.StartWithFlag(
	progress.HideCursor | 
	progress.DisableInput | 
	progress.AutoStop,
)

Note: AutoStop is enabled by default unless overridden.