code: func (s *RepositoriesService) GetKey(ctx context.Context, owner string, repo string, id int64) (*Key, *Response, error) {
  	u := fmt.Sprintf("repos/%v/%v/keys/%v", owner, repo, id)
  
  	req, err := s.client.NewRequest("GET", u, nil)
  	if err != nil {
  		return nil, nil, err
  	}
  
  	key := new(Key)
  	resp, err := s.client.Do(ctx, req, key)
  	if err != nil {
  		return nil, resp, err
  	}
  
  	return key, resp, nil
  }
docs: // GetKey fetches a single deploy key.
  //
  // GitHub API docs: https://developer.github.com/v3/repos/keys/#get