code: func (s *Server) GetRootCACertificate(ctx context.Context, request *api.GetRootCACertificateRequest) (*api.GetRootCACertificateResponse, error) {
  	log.G(ctx).WithFields(logrus.Fields{
  		"method": "GetRootCACertificate",
  	})
  
  	s.signingMu.Lock()
  	defer s.signingMu.Unlock()
  
  	return &api.GetRootCACertificateResponse{
  		Certificate: s.localRootCA.Certs,
  	}, nil
  }
docs: // GetRootCACertificate returns the certificate of the Root CA. It is used as a convenience for distributing
  // the root of trust for the swarm. Clients should be using the CA hash to verify if they weren't target to
  // a MiTM. If they fail to do so, node bootstrap works with TOFU semantics.