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: memfs.go
    path of file: ./repos/trivy/pkg/module
    
    the code of the file until where you have to start completion: package module

import (
	"io"
	"io/fs"
	"path/filepath"
	"time"

	"golang.org/x/xerrors"

	"github.com/aquasecurity/trivy/pkg/mapfs"
	xio "github.com/aquasecurity/trivy/pkg/x/io"
)

// memFS is a wrapper of mapfs.FS and can change its underlying file system
// at runtime. This implements fs.FS.
type memFS struct {
	current *mapfs.FS
}

// Open implements fs.FS.
func (m *memFS) Open(name string) (fs.File, error) {
	if m.current != nil {
		return m.c
    
func (m *memFS) initialize(filePath string, content xio.ReadSeekerAt) error {
	mfs := mapfs.New()
	if err := mfs.MkdirAll(filepath.Dir(filePath), fs.ModePerm); err != nil {
		return xerrors.Errorf("mapfs mkdir error: %w", err)
	}
	b, err := io.ReadAll(content)
	if err != nil {
		return xerrors.Errorf("read error: %w", err)
	}
	err = mfs.WriteVirtualFile(filePath, b, fs.ModePerm)
	if err != nil {
		return xerrors.Errorf("mapfs write error: %w", err)
	}

	m.current = mfs
	return nil
}