How to Use Filesystem Notifications in Go (fsnotify)

Use github.com/fsnotify/fsnotify to create a watcher, add a path, and read events from a channel.

package main

import (
	"fmt"
	"github.com/fsnotify/fsnotify"
)

func main() {
	watcher, err := fsnotify.NewWatcher()
	if err != nil {
		panic(err)
	}
	defer watcher.Close()

	err = watcher.Add("/path/to/dir")
	if err != nil {
		panic(err)
	}

	for {
		select {
		case event, ok := <-watcher.Events:
			if !ok {
				return
			}
			fmt.Println("Event:", event)
		case err, ok := <-watcher.Errors:
			if !ok {
				return
			}
			fmt.Println("Error:", err)
		}
	}
}

fsnotify lets your Go program listen for file changes like edits, deletions, or renames without constantly checking the disk. It works like a security guard who only alerts you when someone actually enters the building, rather than staring at the door all day. You use it when you need your app to react instantly to file updates, such as reloading a config file or rebuilding code.