Somewhat related, I am working on a front end scripting language that implements this idea, but at the runtime layer:

https://hyperscript.org/docs/#async

Basically, the result of every expression is inspected and, if a Promise is returned, the promise is resolved before execution continues. It's all interpreted and really slow for CPU-intensive stuff, but if you are writing async code that isn't CPU intensive it lets you write stuff in the linear manner:

  fetch /message
  put it into my innerHTML

One interesting thing that fell out of that work is that you can have event-driven control flow, like a loop that executes until an event is received by an element:

https://hyperscript.org/docs/#event-control-flow

  <button id="pulsar"
        _="on click repeat until event stop
                      add .pulse then settle
                      remove .pulse then settle
                    end">
    Click me to Pulse...
  </button>