feat(add solutions reference for challenge 01-concurrent-aggregator)

01-context-cancellation-concurrency/01-concurrent-aggregator/order/order.go

@@ -0,0 +1,13 @@
+package order
+
+import "context"
+
+type Order struct {
+	Id     int     `json:"id"`
+	UserId int     `json:"user_id"`
+	Cost   float64 `json:"cost"`
+}
+
+type Service interface {
+	GetAll(ctx context.Context, userId int) ([]*Order, error)
+}