code: func (cli *Client) NetworkConnect(ctx context.Context, networkID, containerID string, config *network.EndpointSettings) error {
  	nc := types.NetworkConnect{
  		Container:      containerID,
  		EndpointConfig: config,
  	}
  	resp, err := cli.post(ctx, "/networks/"+networkID+"/connect", nil, nc, nil)
  	ensureReaderClosed(resp)
  	return err
  }
docs: // NetworkConnect connects a container to an existent network in the docker host.