code: func (s *UsersService) GetGPGKey(ctx context.Context, id int64) (*GPGKey, *Response, error) {
  	u := fmt.Sprintf("user/gpg_keys/%v", id)
  	req, err := s.client.NewRequest("GET", u, nil)
  	if err != nil {
  		return nil, nil, err
  	}
  
  	key := &GPGKey{}
  	resp, err := s.client.Do(ctx, req, key)
  	if err != nil {
  		return nil, resp, err
  	}
  
  	return key, resp, nil
  }
docs: // GetGPGKey gets extended details for a single GPG key. It requires authentication
  // via Basic Auth or via OAuth with at least read:gpg_key scope.
  //
  // GitHub API docs: https://developer.github.com/v3/users/gpg_keys/#get-a-single-gpg-key