Test using custom runtime Lambda for .NET Core 3.1
Related issue: aws/aws-lambda-dotnet#585
native Lambda .NET Core 3.1 support? aws/aws-lambda-dotnet#554
https://aws.amazon.com/blogs/developer/announcing-amazon-lambda-runtimesupport/ https://aws.amazon.com/blogs/developer/net-core-3-0-on-lambda-with-aws-lambdas-custom-runtime/ https://richardballard.co.uk/aws-lambda-function-for-dotnet-3.1-using-custom-runtime/ https://medium.com/@dimoss/asp-net-core-2-2-3-0-serverless-web-apis-in-aws-lambda-with-a-custom-runtime-and-lambda-warmer-ce19ce2e2c74