Initialize Database from middleware

AbstractAsyncInitializationMiddleware.cs

    public abstract class AbstractAsyncInitializationMiddleware
    {
        private readonly RequestDelegate next;
        private readonly ILogger logger;
        private Task initializationTask;

        // ReSharper disable AccessToModifiedClosure
        protected AbstractAsyncInitializationMiddleware(RequestDelegate next, IApplicationLifetime lifetime, ILogger logger)
        {
            this.next = next;
            this.logger = logger;

            var startRegistration = default(CancellationTokenRegistration);
            startRegistration = lifetime.ApplicationStarted.Register(() =>
            {
                initializationTask = InitializeAsync(lifetime.ApplicationStopping);
                startRegistration.Dispose();
            });
        }

        protected abstract Task InitializeAsync(CancellationToken cancellationToken);

        [UsedImplicitly]
        public async Task Invoke(HttpContext context)
        {
            var task = initializationTask;
            if (task != null)
            {
                await task;
                initializationTask = null;
            }

            await next(context);
        }
    }

DatabaseInitializationMiddleware.cs

    // ReSharper disable SuggestBaseTypeForParameter
    public class DatabaseInitializationMiddleware : AbstractAsyncInitializationMiddleware
    {
        private readonly IdentityContext identityContext;
        private readonly DataContext dbContext;

        public DatabaseInitializationMiddleware(
            RequestDelegate next,
            IApplicationLifetime lifetime,
            ILogger<DatabaseInitializationMiddleware> logger,
            IdentityContext identityContext,
            DataContext dbContext) : base(next, lifetime, logger)
        {
            this.identityContext = identityContext;
            this.dbContext = dbContext;
        }

        protected override async Task InitializeAsync(CancellationToken cancellationToken)
        {
            if (OperatingEnvironment.IsWindows())
            {
                await identityContext.Database.MigrateAsync(cancellationToken);
                await dbContext.Database.MigrateAsync(cancellationToken);
            }
            else
            {
                await identityContext.Database.EnsureCreatedAsync(cancellationToken);
                await dbContext.Database.EnsureCreatedAsync(cancellationToken);
            }
        }
    }