Regex Search / Replace with substitutions in Go

regex-substitution.go

// https://go.dev/play/p/XPjAjsNm_2H
package main

import (
	"fmt"
	"regexp"
)

func main() {
	source := "http://some.dumb.domain/path/to/resource/12345"
	regex := "^(?P<scheme>(http)|(https))://(?P<host>[^/]+)(?P<path>/.*/)(?P<id>[^/]+)$"
	template := "From Source - scheme:${scheme} host:${host} path:${path} id:${id} or 1:${1} 4:${4} 5:${5} 6:${6}"

	rxp := regexp.MustCompile(regex)
	var result string
	if matches := rxp.FindStringSubmatchIndex(source); len(matches) > 0 {
		result = string(rxp.ExpandString(nil, template, source, matches))
	}
	fmt.Println(result)
}