Async Rust Web Performance

I was watching thePrimeagen's latest video in which he compares performance between a Rust, Typescript, and Go version of a game server. In it, the Rust version's performance seesaws wildly while the Go one stays stable, and I figure it's because async Rust is hard to do well.

I was wondering if anyone with more async Rust experience here might be willing to take a look at it. Code is here. Bonus points if y'all know any good resources on writing good async Rust.