Server-Sent Events on AWS Lambda with dotnet and AWS API Gateway

[Luke-1988]

Hi! AWS has recently announced support for response streaming in AWS API Gateway. I am using AWS Lambda on dotnet with ASP.NET using following pattern

public class LambdaEntryPoint : APIGatewayProxyFunction
{
    protected override void Init(IWebHostBuilder builder)
    {
        builder
            .UseStartup<Startup>();
    }
}

This works when using Buffered integration type between AWS API Gateway and AWS Lambda, however once integration type is changed to Stream then I have

{"message": "Internal server error"}

Is there some error on my end or this is not yet implemented? In that case is it somewhere on the roadmap?

Thanks