code: func (h *Client) rollback(ctx context.Context, req *rls.RollbackReleaseRequest) (*rls.RollbackReleaseResponse, error) {
  	c, err := h.connect(ctx)
  	if err != nil {
  		return nil, err
  	}
  	defer c.Close()
  
  	rlc := rls.NewReleaseServiceClient(c)
  	return rlc.RollbackRelease(ctx, req)
  }
docs: // rollback executes tiller.RollbackRelease RPC.