Golang find string sub groups match using regex

matches.go

package main

import (
	"fmt"
	"regexp"
)

func main() {
	regex := regexp.MustCompile(`^([0-9]+)|([a-z]+)$`)
	matches := regex.FindAllString("100mb", -1)

	fmt.Println(matches[0]) // 100
	fmt.Println(matches[1]) // mb
}