code: func (pf *PortForwarder) GetPorts() ([]ForwardedPort, error) {
  	if pf.Ready == nil {
  		return nil, fmt.Errorf("no Ready channel provided")
  	}
  	select {
  	case <-pf.Ready:
  		return pf.ports, nil
  	default:
  		return nil, fmt.Errorf("listeners not ready")
  	}
  }
docs: // GetPorts will return the ports that were forwarded; this can be used to
  // retrieve the locally-bound port in cases where the input was port 0. This
  // function will signal an error if the Ready channel is nil or if the
  // listeners are not ready yet; this function will succeed after the Ready
  // channel has been closed.