Air — Live Reload for Go Applications

What it is

Air is a live-reload utility for Go applications. It monitors your project directory with fsnotify, and every time a .go file changes it rebuilds the project and restarts the binary automatically. This brings the instant feedback loop common in JavaScript (nodemon) and Python (Flask debug mode) to Go development.

Air is aimed at Go backend developers who want faster iteration cycles during local development. It supports custom build commands, file exclusion patterns, colored log output, and proxy mode for web frameworks.

How it saves time or tokens

Without Air, every code change requires manually stopping the server, running go build, and restarting. Air collapses this into a single save action. It handles debouncing (multiple rapid saves trigger only one rebuild), displays build errors inline without crashing, and forwards signals like SIGINT so graceful shutdown works correctly.

For teams using AI coding assistants that write and edit Go files, Air keeps the running server always in sync with the latest code without manual intervention.

How to use

1. Install Air:

go install github.com/air-verse/air@latest

1. Initialize the config file in your project root:

air init

This creates .air.toml with sensible defaults.

1. Start watching:

air

Air now rebuilds and restarts on every file change.

Example

Minimal .air.toml configuration:

root = '.'
tmp_dir = 'tmp'

[build]
cmd = 'go build -o ./tmp/main .'
bin = './tmp/main'
watch = ['.']
exclude_dir = ['assets', 'tmp', 'vendor', 'node_modules']
include_ext = ['go', 'tpl', 'tmpl', 'html']
delay = 1000  # ms debounce

[log]
color = true

Or run without any config file:

air --build.cmd 'go build -o ./tmp/main .' --build.bin './tmp/main'

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Common pitfalls

• Air watches the current directory by default. If your main package is in a subdirectory, set root in .air.toml or run Air from that directory.
• On macOS, fsnotify may hit the default file descriptor limit with large projects. Increase it with ulimit -n 10240 if Air misses changes.
• Air does not run tests automatically. Pair it with a separate test watcher if you want test-on-save behavior.