StartFunction.cs

[FunctionName("AsyncHttpFunction")]
public static async Task<IActionResult> RunAsync(
 [HttpTrigger(AuthorizationLevel.Anonymous, "post", Route = null)] HttpRequest req,
 [Orchestration​Client​] IDurableOrchestrationClient starter,
 ILogger log)
{
    string requestBody = await new StreamReader(req.Body).ReadToEndAsync();
    dynamic data = JsonConvert.DeserializeObject(requestBody);
    string instanceId = await starter.StartNewAsync("Orchestration", (int)(data.secondsToWait ?? 60)).ConfigureAwait(false);

    return starter.CreateCheckStatusResponse(req, instanceId);
}