如何编写这些golang和mgo代码

Question

My mongodb data is here

 db.user.aggregate([{$project:{"_id":1,"NoOfUsers":{"$size":"$user"},"NoOfSales":{"$size":"$sales"},"user":1,"sales":1}}]).pretty()
{
    "_id" : ObjectId("57307906f051147d5317984e"),
    "user" : [
        {
            "firstName" : "chetan",
            "lastName" : "kumar",
            "age" : 23
        },
        {
            "firstName" : "nepolean",
            "lastName" : "dang",
            "age" : 26
        },
        {
            "firstName" : "Raj",
            "lastname" : "kumar",
            "age" : 26
        }
    ],
    "sales" : [
        {
            "firstName" : "ashu",
            "lastName" : "jha",
            "age" : 27
        }
    ],
    "NoOfUsers" : 3,
    "NoOfSales" : 1
}

I try to write these code in golang , here is my golang code

package main

import(
    "fmt"
    "log"
    "net/http"
        "encoding/json"
    "github.com/gorilla/mux"
        "gopkg.in/mgo.v2"
        "gopkg.in/mgo.v2/bson"
)
type User struct{
    FIRSTNAME   string      `json:"firstName" bson:"firstName"`
    LASTNAME    string      `json:"lastName" bson:"lastName"`
    AGE     int     `json:"age" bson:"age"`
}
type Sales struct{
    FIRSTNAME   string      `json:"firstName" bson:"firstName"`
    LASTNAME    string      `json:"lastName" bson:"lastName"`
    AGE     int     `json:"age" bson:"age"`
}

type Details struct{
    ID  bson.ObjectId   `json:"_id" bson:"_id"`
    USER    []User      `json:"user" bson:"user"`
    SALES   []Sales     `json:"sales" bson:"sales"`
}
func detail(w http.ResponseWriter, r *http.Request){
    session, err := mgo.Dial("127.0.0.1")
        if err != nil {
                panic(err)
        }else{
                fmt.Println("dial")
        }
        defer session.Close()


        session.SetMode(mgo.Monotonic, true)

        c := session.DB("userdb").C("user")


       var result []Details


    o1 := bson.M{"$project":bson.M{"_id":1,"NoOfUser":bson.M{"$size":"$user"},"user":1,"NoOfSales":bson.M{"$size":"$sales"},"sales":1,},}

        operations := []bson.M{o1}
    pipe := c.Pipe(operations)
    err = pipe.All(&result)
        if err != nil {
                log.Fatal(err)
        }
        res1B, _ := json.Marshal(result)
        fmt.Fprintf(w,string(res1B))
}

func main(){
    router := mux.NewRouter().StrictSlash(true)
    router.HandleFunc("/detail",detail)
    log.Fatal(http.ListenAndServe(":9080", router))

}

After executing this code my result is like this

[{"_id":"57307906f051147d5317984e","user":[{"firstName":"chetan","lastName":"kumar","age":23},{"firstName":"nepolean","lastName":"dang","age":26},{"firstName":"Raj","lastName":"","age":26}],"sales":[{"firstName":"ashu","lastName":"jha","age":27}]}]

Problem is ,it does not show the NoOfusers and NoOfsales ,So is this possible to print the same output as present in above mongodb result without using any extra struct field like NoOfusers or NoOfsales

Answer 1

If you just want to print the result without any mapping from Details struct, then replace var result []Details with var result []bson.M.

If you want to map into Details, then you need to add a struct for the two fields into Details.