[CookiesOnMyDesk]

Something like this, depending on how you want your input and output to be supplied.

    public async IAsyncEnumerable<HttpResponseMessage> SendTwelveRequestsAtATimeAsync(IAsyncEnumerable<HttpRequestMessage> requests)
    {
        HttpClient client = new();
        List<HttpRequestMessage> requestsBatch = [];

        await foreach (var req in requests)
        {
            if (requestsBatch.Count < 12)
            {
                requestsBatch.Add(req);
            }
            else
            {
                foreach (var res in await Task.WhenAll(requestsBatch.Select(client.SendAsync)))
                {
                    yield return res;
                }

                requestsBatch = [];
            }
        }
    }

[ahoka]

I would not call this trivial. :)

[com2kid]

I'd argue that it is a lot easier than doing it with threads!

Promises are a primitive, and async and await keywords in JavaScript is just syntactic sugar around promises (it is sugar around similar constructs in other languages). A promise being just a long running task that will return a result eventually. Being able to grab a promise as an object and pass it around is super useful at times, and it is something I end up using a lot in my JS/TS code.

Because it is a language primitive that is also expressed in the type system, more complex systems can safely be built up around it, in the same way that it is easier to build safe(r) complex systems up around threads in languages that have threads as a primitive. (Rust being a great example here of bringing threads into the language, Java being another early example, though their early attempts were not perfect since we've learned a lot since 1995!)

Async/await and promises are a great example of a technology that makes doing easy stuff easy, and makes hard stuff possible.

tl;dr people need to stop complaining that other multitasking/threading paradigm looks different than their preferred one, each has plusses and minuses and one isn't "better" than others, they just serve different purposes.