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: apk.go
    path of file: ./repos/trivy/pkg/fanal/analyzer/repo/apk
    
    the code of the file until where you have to start completion: package apk

import (
	"bufio"
	"context"
	"os"
	"regexp"

	"golang.org/x/exp/slices"
	"golang.org/x/xerrors"

	ver "github.com/aquasecurity/go-version/pkg/version"
	"github.com/aquasecurity/trivy/pkg/fanal/analyzer"
	"github.com/aquasecurity/trivy/pkg/fanal/types"
)

func init() {
	analyzer.RegisterAnalyzer(&apkRepoAnalyzer{})
}

const version = 1
const edgeVersion = "edge"

var (
	requiredFiles  = []string{"etc/apk/repositories"}
	urlParseRegexp = regexp.MustCompile(`(https*|ftp)://[0-9A-Za-z.-]+/([A-Za-z]+)/v?([0-9A-Za-z_.-]+)/`)
)

type apkRepoAnalyzer struct{}

func (a apkRepoAnalyzer) Analyze(_ context.Co
    
func (a apkRepoAnalyzer) Analyze(_ context.Context, input analyzer.AnalysisInput) (*analyzer.AnalysisResult, error) {
	scanner := bufio.NewScanner(input.Content)
	var osFamily types.OSType
	var repoVer string
	for scanner.Scan() {
		line := scanner.Text()

		m := urlParseRegexp.FindStringSubmatch(line)
		if len(m) != 4 {
			continue
		}

		newOSFamily := types.OSType(m[2])
		newVersion := m[3]

		// Find OS Family
		if osFamily != "" && osFamily != newOSFamily {
			return nil, xerrors.Errorf("mixing different distributions in etc/apk/repositories: %s != %s", osFamily, newOSFamily)
		}
		osFamily = newOSFamily

		// Find max Release version
		switch {
		case repoVer == "":
			repoVer = newVersion
		case repoVer == edgeVersion || newVersion == edgeVersion:
			repoVer = edgeVersion
		default:
			oldVer, err := ver.Parse(repoVer)
			if err != nil {
				continue
			}
			newVer, err := ver.Parse(newVersion)
			if err != nil {
				continue
			}

			// Take the maximum version in apk repositories
			if newVer.GreaterThan(oldVer) {
				repoVer = newVersion
			}
		}
	}

	// Currently, we support only Alpine Linux in apk repositories.
	if osFamily != types.Alpine || repoVer == "" {
		return nil, nil
	}

	return &analyzer.AnalysisResult{
		Repository: &types.Repository{
			Family:  osFamily,
			Release: repoVer,
		},
	}, nil
}