Xin Dong

Just wanna clarify that, according to my local tests, `mongo-go-driver:v1.0.2` does work with both server 3.0 and 3.2.

I tested the latest `MongoKitten` lib by running some basic operations and it just worked fine. Will open PR today or tomorrow.

Maybe we can at least emit a warning (console warning message or an actual complier warning or both) from ActorCompiler if it sees this pattern.

>What is the definition of priority in the above example? Does it mean that `wait` in the `when` condition should have higher priority than the `wait` inside the when statement?...

While PGO is definitely an interesting optimization option to explore, I want to point out that based on the perf gain shown in the preliminary tests above, it might not...