I suspect that a big part of the design of this api (and why it take time) was exactly to be as performant as possible. The compiler desugar the async/await to

I suspect that a big part of the design of this api (and why it take time) was exactly to be as performant as possible. The compiler desugar the async/await to state machines and that is melted away by regular means. Also, the quality of the runtime elected must take some credit.