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: metadata.go
    path of file: ./repos/gitea/modules/packages/goproxy
    
    the code of the file until where you have to start completion: // Copyright 2023 The Gitea Authors. All rights reserved.
// SPDX-License-Identifier: MIT

package goproxy

import (
	"archive/zip"
	"fmt"
	"io"
	"path"
	"strings"

	"code.gitea.io/gitea/modules/util"
)

const (
	PropertyGoMod = "go.mod"

	maxGoModFileSize = 16 * 1024 * 1024 // https://go.dev/ref/mod#zip-path-size-constraints
)

var (
	ErrInvalidStructure  = util.NewInvalidArgumentErrorf("package has invalid structure")
	ErrGoModFileTooLarge = util.NewInvalidArgumentErrorf("go.mod file is too large")
)
    
func ParsePackage(r io.ReaderAt, size int64) (*Package, error) {
	archive, err := zip.NewReader(r, size)
	if err != nil {
		return nil, err
	}

	var p *Package

	for _, file := range archive.File {
		nameAndVersion := path.Dir(file.Name)

		parts := strings.SplitN(nameAndVersion, "@", 2)
		if len(parts) != 2 {
			continue
		}

		versionParts := strings.SplitN(parts[1], "/", 2)

		if p == nil {
			p = &Package{
				Name:    strings.TrimSuffix(nameAndVersion, "@"+parts[1]),
				Version: versionParts[0],
			}
		}

		if len(versionParts) > 1 {
			// files are expected in the "root" folder
			continue
		}

		if path.Base(file.Name) == "go.mod" {
			if file.UncompressedSize64 > maxGoModFileSize {
				return nil, ErrGoModFileTooLarge
			}

			f, err := archive.Open(file.Name)
			if err != nil {
				return nil, err
			}
			defer f.Close()

			bytes, err := io.ReadAll(&io.LimitedReader{R: f, N: maxGoModFileSize})
			if err != nil {
				return nil, err
			}

			p.GoMod = string(bytes)

			return p, nil
		}
	}

	if p == nil {
		return nil, ErrInvalidStructure
	}

	p.GoMod = fmt.Sprintf("module %s", p.Name)

	return p, nil
}