Check if string is int

As you said, you can use strconv.Atoi for this.

if _, err := strconv.Atoi(v); err == nil {
    fmt.Printf("%q looks like a number.\n", v)
}

You could use scanner.Scanner (from text/scanner) in mode ScanInts, or use a regexp to validate the string, but Atoi is the right tool for the job.