code: func (s *FileStorage) LoadUser(email string) (*UserData, error) {
  	var err error
  	userData := new(UserData)
  	userData.Reg, err = s.readFile(s.userRegFile(email))
  	if err != nil {
  		return nil, err
  	}
  	userData.Key, err = s.readFile(s.userKeyFile(email))
  	if err != nil {
  		return nil, err
  	}
  	return userData, nil
  }
docs: // LoadUser implements Storage.LoadUser by loading it from disk. If it is not
  // present, an instance of ErrNotExist is returned.