code: func (s *RepositoriesService) GetPermissionLevel(ctx context.Context, owner, repo, user string) (*RepositoryPermissionLevel, *Response, error) {
  	u := fmt.Sprintf("repos/%v/%v/collaborators/%v/permission", owner, repo, user)
  	req, err := s.client.NewRequest("GET", u, nil)
  	if err != nil {
  		return nil, nil, err
  	}
  
  	rpl := new(RepositoryPermissionLevel)
  	resp, err := s.client.Do(ctx, req, rpl)
  	if err != nil {
  		return nil, resp, err
  	}
  	return rpl, resp, nil
  }
docs: // GetPermissionLevel retrieves the specific permission level a collaborator has for a given repository.
  // GitHub API docs: https://developer.github.com/v3/repos/collaborators/#review-a-users-permission-level