如何移除golang mongodb群组聚合中的嵌套字段？

package main

import (
    "context"
    "fmt"
    "log"

    "go.mongodb.org/mongo-driver/bson"
    "go.mongodb.org/mongo-driver/mongo"
    "go.mongodb.org/mongo-driver/mongo/options"
)

func main() {
    // 创建MongoDB客户端
    clientOptions := options.Client().ApplyURI("mongodb://localhost:27017")
    client, err := mongo.Connect(context.TODO(), clientOptions)
    if err != nil {
        log.Fatal(err)
    }

    // 选择数据库和集合
    collection := client.Database("mydb").Collection("mycollection")

    // 创建聚合管道
    pipeline := mongo.Pipeline{
        {{"$project", bson.D{{"nestedField", 0}}}},
    }

    // 执行聚合操作
    cursor, err := collection.Aggregate(context.TODO(), pipeline)
    if err != nil {
        log.Fatal(err)
    }

    // 处理聚合结果
    var results []bson.M
    if err := cursor.All(context.TODO(), &results); err != nil {
        log.Fatal(err)
    }

    // 输出结果
    for _, result := range results {
        fmt.Println(result)
    }
}

go get go.mongodb.org/mongo-driver/mongo