code: func (ds *dockerService) Exec(_ context.Context, req *runtimeapi.ExecRequest) (*runtimeapi.ExecResponse, error) {
  	if ds.streamingServer == nil {
  		return nil, streaming.NewErrorStreamingDisabled("exec")
  	}
  	_, err := checkContainerStatus(ds.client, req.ContainerId)
  	if err != nil {
  		return nil, err
  	}
  	return ds.streamingServer.GetExec(req)
  }
docs: // Exec prepares a streaming endpoint to execute a command in the container, and returns the address.