code: func (*Instances) Get(c context.Context, req *instances.GetRequest) (*instances.Instance, error) {
  	switch {
  	case req.GetId() == "" && req.GetHostname() == "":
  		return nil, status.Errorf(codes.InvalidArgument, "ID or hostname is required")
  	case req.Id != "" && req.Hostname != "":
  		return nil, status.Errorf(codes.InvalidArgument, "exactly one of ID or hostname is required")
  	case req.Id != "":
  		return getByID(c, req.Id)
  	default:
  		return getByHostname(c, req.Hostname)
  	}
  }
docs: // Get handles a request to get an existing instance.