main.go

package main

import (
	"context"
	"log"

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

func main() {
	clientOptions := options.Client().
		ApplyURI("mongodb://127.0.0.1:8000/?loadBalanced=true").
		SetLoadBalanced(true).
		SetMaxPoolSize(3)

	ctx := context.Background()

	client, err := mongo.Connect(ctx, clientOptions)
	if err != nil {
		log.Fatalf("error connecting to MongoDB: %v", err)
	}

	defer client.Disconnect(context.Background())

	coll := client.Database("db").Collection("test")
	coll.InsertOne(ctx, bson.D{{"x", 1}})
	coll.InsertOne(ctx, bson.D{{"x", 2}})
	coll.InsertOne(ctx, bson.D{{"x", 3}})

	for i := 0; i < 4; i++ {
		find(ctx, client.Database("db"))
	}
}

func find(ctx context.Context, db *mongo.Database) {
	_, err := db.RunCommandCursor(ctx, bson.D{
		{"find", "test"}, // Collection
		{"batchSize", 1},
		{"filter", bson.D{{"x", bson.D{{"$gte", 0}}}}},
	})
	if err != nil {
		panic(err)
	}
}