Clojure core.async go blocks use an analyzer to rewrite code with inversion of control specifically for channel parking operations (the ! async ops like >!). Other blocking operations (!! channel ops or arbitrary I/O ops) are not allowed. Additionally, go blocks are automatically collected if the channels they depend on are collected (and parking can never progress).

The Java 21 virtual threads feature implements I/O parking in the Java platform itself - that capability is a superset of what go blocks provide by supporting all blocking I/O operations. Like regular threads, (and unlike go blocks) virtual threads must terminate ordinarily and will keep referenced resources alive until they do.

Due to this difference in semantics, go blocks are unchanged and continue to use the go analyzer and run on platform threads. If you wish to get the benefits and constraints of virtual threads, convert go to io-thread and parking ops to blocking ops.

Note: existing IOC compiled go blocks from older core.async versions are unaffected.