pkg/modtimevfs/modtimevfs.go
func New(fs http.FileSystem, t time.Time) http.FileSystem {
	return &timefs{fs: fs, t: t}
}
func New(fs http.FileSystem, t time.Time) http.FileSystem {
	return &timefs{fs: fs, t: t}
}
// New returns a file system that returns constant modification time for all files.