package main

import (
	"context"
	"fmt"
	"go.mongodb.org/mongo-driver/bson"
	"go.mongodb.org/mongo-driver/mongo"
	"go.mongodb.org/mongo-driver/mongo/options"
	"log"
	"sync"
	"time"
)

func main() {
	client, err := mongo.NewClient(options.Client().ApplyURI("mongodb://localhost:27017"))
	if err != nil {
		log.Fatal("failed to build client", err)
	}
	err = client.Connect(context.Background())
	if err != nil {
		log.Fatal("failed to connect", err)
	}

	coll := client.Database("test").Collection("test")
	wg := sync.WaitGroup{}
	for i := 0; i < 50; i++ {
		wg.Add(1)
		go func() {
			defer wg.Done()
			cursor, err := coll.Watch(context.Background(), bson.D{})
			if err != nil {
				log.Fatal("failed to watch: ", err)
			}
			defer cursor.Close(context.Background())

			// consume the cursor but bail out after 5 sec
			ctx, _ := context.WithTimeout(context.Background(), 5*time.Second)
			_ = cursor.Next(ctx)
			fmt.Println("err", cursor.Err())
		}()
	}

	wg.Wait()
	for {
		fmt.Println("now sleeping here")
		time.Sleep(time.Second)
	}
}