static async Task Main(string[] args)
{
Console.WriteLine("a");
await TestFunc();
Console.WriteLine("f");
}

public static async Task TestFunc()
{
Console.WriteLine("b");
await Task.Run(() =>
{
Console.WriteLine("c");
string s = "";
for (var i = 0; i < 100000; i++)
{
s += "a";
}
Console.WriteLine("d");
});
Console.WriteLine("e");
}
>>650