Using AsyncStreams to call a web service

.Net Core 3.0 includes Asynchronous streams.   

Basically IAsyncEnumerable<T> is an asynchronous version of IEnumerable<T>.   To use it in a you await a foreach loop to consume the elements

await foreach (var location in GetISSLocationSequence())
{
    Console.WriteLine(location);
}

GetISSLocationSequence is an async function which yield 20 IIS locations.  

It waits 1 second between getting locations

public static async System.Collections.Generic.IAsyncEnumerable<string> GetISSLocationSequence()
{
    using HttpClient http = new HttpClient();
    for (int i = 0; i < 20; i++)
    {
        var json = await http.GetStringAsync("http://api.open-notify.org/iss-now.json");
        await Task.Delay(2000);
        yield return json;
    }
}

One other thing I would like to point out was the format for the using 

statement.  Notice in this function I am using a using statement to make 

sure the HtppClient get disposed of when we done with it.  Notice we no 

long have to put the code is {}.  The HttpClient will dispose at the end 

of the function

To demo this I put the code in a .net core console application.  To allow 
await in the sub main I changed it from a void to async Task


class Program
{
    static async Task Main(string[] args)
    {
  
        await foreach (var location in GetISSLocationSequence())
        {
            Console.WriteLine(location);
        }
    }