Using Feature Flags and Externalized configuration .NET Core app with Flagsmith - 2

Feature_flags_with_Flagsmith-2.cs

public class BulletTrainRemoteConfiguration : IRemoteConfiguration
{
    private readonly string _userIdentity;
    private static readonly object LockObject = new object();        

    public BulletTrainRemoteConfiguration(RemoteConfigurationSettings settings)
    {
        if (BulletTrainClient.instance == null)
            lock (LockObject)
                if (BulletTrainClient.instance == null)
                {
                    var configuration = new BulletTrainConfiguration
                    {
                        ApiUrl = settings.ApiUrl,
                        EnvironmentKey = settings.EnvironmentKey
                    };
                    var bulletClient = new BulletTrainClient(configuration);
                }
        _userIdentity = settings.ClientAppId;
    }
    
    public async Task<List<Feature>> GetFeatures()
    {
        var flags = await BulletTrainClient.instance.GetFeatureFlags(_userIdentity);
        var features = flags.Select(f => new Feature
        {
            Name = f.GetFeature().GetName(),
            Value = f.IsEnabled()
        }).ToList();
        return features;
    }

    public Task<bool> IsFeatureEnabled(string key)
    {
        return BulletTrainClient.instance.HasFeatureFlag(key, _userIdentity);
    }