code: func (s *AuthorizationsService) GetGrant(ctx context.Context, id int64) (*Grant, *Response, error) {
  	u := fmt.Sprintf("applications/grants/%d", id)
  	req, err := s.client.NewRequest("GET", u, nil)
  	if err != nil {
  		return nil, nil, err
  	}
  
  	grant := new(Grant)
  	resp, err := s.client.Do(ctx, req, grant)
  	if err != nil {
  		return nil, resp, err
  	}
  
  	return grant, resp, nil
  }
docs: // GetGrant gets a single OAuth application grant.
  //
  // GitHub API docs: https://developer.github.com/v3/oauth_authorizations/#get-a-single-grant