Query using $lookup works in shell, but not in the code

I am using golang and mongo db for my backend.
I have transactions collection, which has the following structure.

{ "_id" : ObjectId("63d91a96940d4d147b32182a"), "category" : ObjectId("63caf0bccdb235dda38b4859"), "amount" : "1000", "owner" : ObjectId("63d3c9957bc044d051e01021"), "invdt" : ISODate("2022-10-11T00:00:00Z"), "date" : "2022-10-11" }

I need to insert data from category collection by corresponding _id.
The following query works properly in the mongo shell, but not in the code itself

db.transactions.aggregate([{$lookup:{from:"categories",localField:"category",foreignField:"_id",as:"cat"}}])

In the code, i try to get data by the following code

type Transaction struct {
	ID       primitive.ObjectID `json:"id" bson:"_id"`
	Category primitive.ObjectID `bson:"category,omitempty" json:"category"`
	Amount   string             `json:"amount" binding:"required"`
	Owner    primitive.ObjectID `bson:"owner,omitempty" json:"owner"`
	InvDt    primitive.DateTime `bson:"invdt,omitempty" json:"invdt,omitempty"`
	Date     string             `json:"date" binding:"required"`
}

pipeline := mongo.Pipeline{
    {{"$match", bson.D{
	  {"owner", bson.D{
	  {"$eq", user.ID},},},
		}}},
		{{"$lookup", bson.D{
			{"from", "categories"},
			{"localField", "category"},
			{"foreignField", "_id"},
			{"as", "cat"},
		}}},
	}
    cur, err := handler.collection.Aggregate(handler.ctx, pipeline)
    defer cur.Close(handler.ctx)
	transactions := make([]models.Transaction, 0)

	for cur.Next(handler.ctx) {
		var transaction models.Transaction
		cur.Decode(&transaction)
		transactions = append(transactions, transaction)
	}


c.JSON(http.StatusOK, transactions)

I've tried without $match, but it doesn't help much.
For some reason $lookup doesn't work

Result from query in the mongo shell

{ "_id" : ObjectId("63d919f71ee94b0bdfea593a"), "category" : ObjectId("63caf0bccdb235dda38b4859"), "amount" : "1000", "owner" : ObjectId("63d3c9957bc044d051e01021"), "invdt" : ISODate("2022-10-11T00:00:00Z"), "date" : "2022-10-11", "cat" : [ { "_id" : ObjectId("63caf0bccdb235dda38b4859"), "name" : "Food2", "type" : "Expense", "owner" : ObjectId("63caf08ccdb235dda38b4857") } ] }
{ "_id" : ObjectId("63d91a96940d4d147b32182a"), "category" : ObjectId("63caf0bccdb235dda38b4859"), "amount" : "1000", "owner" : ObjectId("63d3c9957bc044d051e01021"), "invdt" : ISODate("2022-10-11T00:00:00Z"), "date" : "2022-10-11", "cat" : [ { "_id" : ObjectId("63caf0bccdb235dda38b4859"), "name" : "Food2", "type" : "Expense", "owner" : ObjectId("63caf08ccdb235dda38b4857") } ] }

Here appears a new field cat with populated data from categories collection.
In the request from the postman, I don't get this field

The problem was in the struct Transaction.
There was no corresponding field

Cat []map[string]interface{} `json:"cat" bson:"cat"`

type Transaction struct {
	ID       primitive.ObjectID       `json:"id" bson:"_id"`
	Category primitive.ObjectID       `bson:"category,omitempty" json:"category"`
	Amount   string                   `json:"amount" binding:"required"`
	Owner    primitive.ObjectID       `bson:"owner,omitempty" json:"owner"`
	InvDt    primitive.DateTime       `bson:"invdt,omitempty" json:"invdt,omitempty"`
	Date     string                   `json:"date" binding:"required"`
	Cat      []map[string]interface{} `json:"cat" bson:"cat"`
}