$ oto中的$ dateToString不起作用

Question

I wrote the code in Go. I have a mongodb query in mgo that has made me busy for 3 days and still fighting with it.

Though a query with mongo shell works, mongodb query with mgo does not work.

Below query and result are made with mongo shell.

// Query
db.getCollection("TEST").aggregate([
{
    "$match": {
        "date": {"$gte": new Date("2016-06-28"), "$lte": new Date("2016-06-29")},
    }
},
{
    "$project": {
        "_id": false,
        "date": {"$dateToString": {"format": "%Y%m%d", "date":"$date"}},
    },
},
]);


// Result
{
"date" : "20160628",
}
{
"date" : "20160629",
}

Below query and result are made with mgo. It doesn't work.

// Query
matchQuery := bson.M{}
matchQuery["date"] = bson.M{
    "$gte": time.Date(2016, 6, 28, 0, 0, 0, 0, time.UTC),
    "$lte": time.Date(2016, 6, 29, 23, 59, 59, 0, time.UTC),
}
projectQuery := bson.M{
    "_id": false,
    "date": bson.M{
        "$dateToString": bson.M{"format": "%Y%m%d", "date": "$date"},
    },
}
pipeline := []bson.M{
    {"$match": matchQuery},
    {"$project": projectQuery},
}


// Result
{
    "date": "0001-01-01T00:00:00Z",
},

{
    "date": "0001-01-01T00:00:00Z",
}

How can I work $dateToString correctly?

Answer 1

I solved it. It was my mistake. I post the answer so that anyone does not make a mistake like me. I didn't change variable type from "time.Time" to "string" like below.

//Old
type content struct {
    Date  time.Time `bson:"date" json:"date"`
}

//New
type content struct {
    Date  string `bson:"date" json:"date"`
}

Thanks :)