You need to add to go keyword to change a normal function to a goroutine. If you would remove async/await and Task/Return from the C# code example, it would perform pretty much the same as Go.

If you want to show that async/await calls are expensive, than you should have shown two code samples of C#, one with async/await, and one without.

Or could have done the same for Go, show one example with goroutines, and one without.

But I think everyone already know that async/await and goroutines has it's costs.

The problem is more that you are comparing Go without goroutines (without it's allocation costs) to a C# example with a poor implementation of async/await.