Go language how detect file changing?

Here’s a simple cross-platform version:

func watchFile(filePath string) error {
    initialStat, err := os.Stat(filePath)
    if err != nil {
        return err
    }

    for {
        stat, err := os.Stat(filePath)
        if err != nil {
            return err
        }

        if stat.Size() != initialStat.Size() || stat.ModTime() != initialStat.ModTime() {
            break
        }

        time.Sleep(1 * time.Second)
    }

    return nil
}

And usage would be like this:

doneChan := make(chan bool)

go func(doneChan chan bool) {
    defer func() {
        doneChan <- true
    }()

    err := watchFile("/path/to/file")
    if err != nil {
        fmt.Println(err)
    }

    fmt.Println("File has been changed")
}(doneChan)

<-doneChan

Not as efficient as a proper system call but it’s simple and works everywhere, and might be enough for some uses.