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: fs.go
    path of file: ./repos/statik/fs
    
    the code of the file until where you have to start completion: // Copyright 2014 Google Inc. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

// Package fs contains an HTTP file system that works with zip contents.
package fs

import (
	"archive/zip"
	"bytes"
	"errors"
	"fmt"
	"io"
	"io/ioutil"
	"net/http"
	"os"
	"path"
	"path/filepath"
	"sort"
	"strings"
	"time"
)

var zipData = map[string]string{}

// file holds unzipped read-only file contents and file metadata.
type 
    
func NewWithNamespace(assetNamespace string) (http.FileSystem, error) {
	asset, ok := zipData[assetNamespace]
	if !ok {
		return nil, errors.New("statik/fs: no zip data registered")
	}
	zipReader, err := zip.NewReader(strings.NewReader(asset), int64(len(asset)))
	if err != nil {
		return nil, err
	}
	files := make(map[string]file, len(zipReader.File))
	dirs := make(map[string][]string)
	fs := &statikFS{files: files, dirs: dirs}
	for _, zipFile := range zipReader.File {
		fi := zipFile.FileInfo()
		f := file{FileInfo: fi, fs: fs}
		f.data, err = unzip(zipFile)
		if err != nil {
			return nil, fmt.Errorf("statik/fs: error unzipping file %q: %s", zipFile.Name, err)
		}
		files["/"+zipFile.Name] = f
	}
	for fn := range files {
		// go up directories recursively in order to care deep directory
		for dn := path.Dir(fn); dn != fn; {
			if _, ok := files[dn]; !ok {
				files[dn] = file{FileInfo: dirInfo{dn}, fs: fs}
			} else {
				break
			}
			fn, dn = dn, path.Dir(dn)
		}
	}
	for fn := range files {
		dn := path.Dir(fn)
		if fn != dn {
			fs.dirs[dn] = append(fs.dirs[dn], path.Base(fn))
		}
	}
	for _, s := range fs.dirs {
		sort.Strings(s)
	}
	return fs, nil
}