You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: domain_matcher.go
    path of file: ./repos/v2ray-core/common/strmatcher
    
    the code of the file until where you have to start completion: package strmatcher

import "strings"

func breakDomain(domain string) []string {
	return strings.Split(domain, ".")
}

type node struct {
	values []uint32
	sub    map[string]*node
}

// DomainMatcherGroup is a IndexMatcher for a large set of Domain matchers.
// Visible for testing only.
type DomainMatcherGroup struct {
	root *node
}


    
func (g *DomainMatcherGroup) Match(domain string) []uint32 {
	if domain == "" {
		return nil
	}

	current := g.root
	if current == nil {
		return nil
	}

	nextPart := func(idx int) int {
		for i := idx - 1; i >= 0; i-- {
			if domain[i] == '.' {
				return i
			}
		}
		return -1
	}

	matches := [][]uint32{}
	idx := len(domain)
	for {
		if idx == -1 || current.sub == nil {
			break
		}

		nidx := nextPart(idx)
		part := domain[nidx+1 : idx]
		next := current.sub[part]
		if next == nil {
			break
		}
		current = next
		idx = nidx
		if len(current.values) > 0 {
			matches = append(matches, current.values)
		}
	}
	switch len(matches) {
	case 0:
		return nil
	case 1:
		return matches[0]
	default:
		result := []uint32{}
		for idx := range matches {
			// Insert reversely, the subdomain that matches further ranks higher
			result = append(result, matches[len(matches)-1-idx]...)
		}
		return result
	}
}