testapps/TestNativeAotSingleProject/Function.cs

using Amazon.Lambda.Core;
using Amazon.Lambda.RuntimeSupport;
using Amazon.Lambda.Serialization.SystemTextJson;

namespace NativeAotTest;

public class Function
{
    /// <summary>
    /// The main entry point for the custom runtime.
    /// </summary>
    /// <param name="args"></param>
    private static async Task Main(string[] args)
    {
        Func<string, ILambdaContext, string> handler = FunctionHandler;
        await LambdaBootstrapBuilder.Create(handler, new DefaultLambdaJsonSerializer())
            .Build()
            .RunAsync();
    }

    /// <summary>
    /// A simple function that takes a string and does a ToUpper
    ///
    /// To use this handler to respond to an AWS event, reference the appropriate package from 
    /// https://github.com/aws/aws-lambda-dotnet#events
    /// and change the string input parameter to the desired event type.
    /// </summary>
    /// <param name="input"></param>
    /// <param name="context"></param>
    /// <returns></returns>
    public static string FunctionHandler(string input, ILambdaContext context)
    {
        return input.ToUpper();
    }
}