TracingOptions

current.cs

// this is what an output binding approach would do
// downsides are that everything added is only resolved once the execution finishes
// so the timestamps and stuff may be bad

namespace Company.Function
{

    public class HttpTrigger
    {
        [FunctionName("HttpTrigger")]
        public static async Task<IActionResult> Run(
            [HttpTrigger(AuthorizationLevel.Anonymous, "get", "post", Route = null)] HttpRequest req,
            [NewRelic("telemetryThing")] IAsyncCollector<TraceConfigProvider> _traceProvider)
        {
            await _traceProvider.AddAsync("foo");

            return new OkObjectResult(responseMessage);
        }
    }
}

recommended.cs

// this is what an output binding approach would do
// it now is just using your TelemetryClient directly, and user just needs
// to create a constructor and they'd be set.  This is pulling out the service you register in your
// `Startup.cs` of the extension

namespace Company.Function
{
    private readonly TraceConfigProvider _traceProvider;
    public class HttpTrigger(TelemetryClient provider)
    {
        _traceProvider = provider.Create();
    }

    public class HttpTrigger
    {
        [FunctionName("HttpTrigger")]
        public static async Task<IActionResult> Run(
            [HttpTrigger(AuthorizationLevel.Anonymous, "get", "post", Route = null)] HttpRequest req)
        {
            _traceProvider.trace("foo");

            return new OkObjectResult(responseMessage);
        }
    }
}