code: func NewFilesystemStore(path string, keyPairs ...[]byte) *FilesystemStore {
  	if path == "" {
  		path = os.TempDir()
  	}
  	fs := &FilesystemStore{
  		Codecs: securecookie.CodecsFromPairs(keyPairs...),
  		Options: &Options{
  			Path:   "/",
  			MaxAge: 86400 * 30,
  		},
  		path: path,
  	}
  
  	fs.MaxAge(fs.Options.MaxAge)
  	return fs
  }
docs: // NewFilesystemStore returns a new FilesystemStore.
  //
  // The path argument is the directory where sessions will be saved. If empty
  // it will use os.TempDir().
  //
  // See NewCookieStore() for a description of the other parameters.