syntax = "proto3";

package order.v1;
option go_package = "example/gen/order/v1;orderv1";

service OrderService {
  rpc GetOrder(GetOrderRequest) returns (Order);
  rpc WatchOrders(WatchRequest) returns (stream Order);
}

message Order {
  string id = 1;
  int64 amount_cents = 2;
  OrderStatus status = 3;
  reserved 4, 5;
}

ctx, cancel := context.WithTimeout(ctx, 800*time.Millisecond)
defer cancel()

order, err := client.GetOrder(ctx, &orderv1.GetOrderRequest{
  Id: orderID,
})
if err != nil {
  st, ok := status.FromError(err)
  if ok && st.Code() == codes.NotFound { ... }
}

func (s *Server) GetOrder(
  ctx context.Context,
  req *orderv1.GetOrderRequest,
) (*orderv1.Order, error) {
  order, err := s.repo.Find(ctx, req.GetId())
  if errors.Is(err, sql.ErrNoRows) {
    return nil, status.Error(codes.NotFound, "order not found")
  }
  return order, nil
}