Template boilerplate broken

**Describe the bug**
Template tooling is broken

**To Reproduce**

**Expected behavior**
I expect to be given something besides an error message - most probably hit one of the Get endpoints or similar

- Windows Version: 11
- Visual Studio Version: 16.11.7
- AWS Toolkit for Visual Studio Version: 1.23.3.0

**Additional context**
I am new to the whole AWS thing and I am trying to set up an API endpoint to deploy to a lambda. It would be nice if the tooling would work so I could follow along and learn how to do this.

Reproduce the File→New→Project flow for AWS Serverless Application (.NET Core - C#), then inspect APIGatewayProxyFunction.MarshallRequest and AbstractAspNetCoreFunction.FunctionHandlerAsync in the failing stack trace. Done means the generated ASP.NET Core Web API template invokes through Mock Lambda Test Tool and reaches a Get endpoint instead of throwing NullReferenceException.

Written by the indexing model from the issue text.