Azure Functions Dependency Injection "unable to resolve"

using System.Text.Json;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc;
using Microsoft.Azure.Functions.Extensions;
using Microsoft.Azure.Functions.Worker;
using Microsoft.Extensions.Logging;

namespace Bugreporter.API
{
    public class Function1
    {
        private readonly ILogger<Function1> _logger;
        private readonly HelloWorld _helloWorld;

        public Function1(HelloWorld helloWorld, ILogger<Function1> logger)
        {
            _helloWorld = helloWorld;
            _logger = logger;
        }

        [Function("Function1")]
        public async Task<IActionResult> TryRun(
            [HttpTrigger(AuthorizationLevel.Anonymous, "get", "post", Route = null)] HttpRequest req
        )
        {
            _helloWorld.Run();
            try
            {
                ...
            }
            catch (Exception ex)
            {
                string message = "An unexpected error occurred";
                _logger.LogError(ex, message);
                return new StatusCodeResult(StatusCodes.Status500InternalServerError);
            }
        }
    }
}

using System;
using Microsoft.Azure.Functions.Extensions.DependencyInjection;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Logging;

[assembly: FunctionsStartup(typeof(Bugreporter.API.Startup))]

namespace Bugreporter.API;

public class Startup : FunctionsStartup
{
    
    public override void Configure(IFunctionsHostBuilder builder)
    {
        builder.Services.AddSingleton<HelloWorld>();
    }
}

public class HelloWorld
{
   ...

    public void Run()
    {
        _logger.LogInformation("Hello World");
    }
}