code: func (r *RemoteRuntimeService) Exec(req *runtimeapi.ExecRequest) (*runtimeapi.ExecResponse, error) {
  	ctx, cancel := getContextWithTimeout(r.timeout)
  	defer cancel()
  
  	resp, err := r.runtimeClient.Exec(ctx, req)
  	if err != nil {
  		klog.Errorf("Exec %s '%s' from runtime service failed: %v", req.ContainerId, strings.Join(req.Cmd, " "), err)
  		return nil, err
  	}
  
  	if resp.Url == "" {
  		errorMessage := "URL is not set"
  		klog.Errorf("Exec failed: %s", errorMessage)
  		return nil, errors.New(errorMessage)
  	}
  
  	return resp, nil
  }
docs: // Exec prepares a streaming endpoint to execute a command in the container, and returns the address.