code: func (s *AuthorizationsService) Check(ctx context.Context, clientID string, token string) (*Authorization, *Response, error) {
  	u := fmt.Sprintf("applications/%v/tokens/%v", clientID, token)
  
  	req, err := s.client.NewRequest("GET", u, nil)
  	if err != nil {
  		return nil, nil, err
  	}
  
  	a := new(Authorization)
  	resp, err := s.client.Do(ctx, req, a)
  	if err != nil {
  		return nil, resp, err
  	}
  
  	return a, resp, nil
  }
docs: // Check if an OAuth token is valid for a specific app.
  //
  // Note that this operation requires the use of BasicAuth, but where the
  // username is the OAuth application clientID, and the password is its
  // clientSecret. Invalid tokens will return a 404 Not Found.
  //
  // The returned Authorization.User field will be populated.
  //
  // GitHub API docs: https://developer.github.com/v3/oauth_authorizations/#check-an-authorization