code: func WithContext(ctx context.Context, t TestReporter) (*Controller, context.Context) {
  	h, ok := t.(TestHelper)
  	if !ok {
  		h = nopTestHelper{t}
  	}
  
  	ctx, cancel := context.WithCancel(ctx)
  	return NewController(&cancelReporter{h, cancel}), ctx
  }
docs: // WithContext returns a new Controller and a Context, which is cancelled on any
  // fatal failure.