in dotnet-app/src/ServerlessExample/Function.cs [22:30]
private static async Task<string> GetCallingIP()
{
client.DefaultRequestHeaders.Accept.Clear();
client.DefaultRequestHeaders.Add("User-Agent", "AWS Lambda .Net Client");
var msg = await client.GetStringAsync("http://checkip.amazonaws.com/").ConfigureAwait(continueOnCapturedContext:false);
return msg.Replace("\n","");
}