In the Java world, project Loom[1] is hopefully going to end this situation of async code that is hard to use with blocking code. They introduce a concept called Virtual Threads (previously called Fibers, but they are still looking for the perfect name). This will allow for seamless interoperability between blocking and non-blocking code as everything in Java runs on a Thread and Virtual Threads are just a specialization of the concept that doesn't boil down to OS threads.

I haven't used it yet, so I can only repeat the advertising copy, but nevertheless wanted to give some perspective from other ecosystems.

[1]: https://wiki.openjdk.java.net/display/loom/Main