MongoDB 4 concurrent transaction inserts to different collections

Program.cs

using System;
using System.Collections.Generic;
using System.Threading.Tasks;
using MongoDB.Bson;
using MongoDB.Driver;

namespace MongoDB4Concurrency
{
    class Program
    {
        static async Task Main(string[] args)
        {
            var url = new MongoUrl("mongodb://localhost:37017");
            var databaseName = Guid.NewGuid().ToString();
            var client = new MongoClient(url);
            var database = client.GetDatabase(databaseName);

            var documentCount = 1;
            var taskCount = 8;

            var tasks = new List<Task>();

            for (int i = 0; i < taskCount; i++)
            {
                var i1 = i;
                tasks.Add(Task.Run(async () =>
                {
                    var coll = database.GetCollection<BsonDocument>(Guid.NewGuid().ToString());

                    await database.CreateCollectionAsync(coll.CollectionNamespace.CollectionName);

                    using (var session = client.StartSession())
                    {
                        session.StartTransaction();
                        try
                        {
                            for (int j = 0; j < documentCount; j++)
                            {
                                await coll.InsertOneAsync(session, new BsonDocument());
                            }
                            await session.CommitTransactionAsync();

                            Console.WriteLine($"Task {i1}, success");
                        }
                        catch (MongoCommandException e)
                        {
                            Console.WriteLine($"Task {i1}, fail: {e.ErrorMessage}");
                            session.AbortTransaction();
                        }
                    }
                }));
            }

            await Task.WhenAll(tasks);

            Console.WriteLine("Complete");
            new MongoClient(url).DropDatabase(databaseName);
        }
    }
}