> Why would there be paranoia when writing blocking code with async?

In languages like JavaScript, you have to be careful to avoid blocking the event loop, and use something like worker threads for CPU-intensive tasks. Otherwise you will end up with long tail latencies. In Go, the runtime automatically manages this and can suspend and resume long-running goroutines.

> naively accessing a global value can lead to race conditions

Fair point that the language doesn't automatically catch this, but that's what a mutex is for. In return you get actual parallelism that can use all your CPU cores