> It is opt-in. If you're using Tokio then you can specify whether you want to use a single-threaded or multi-threaded runtime. Multi-threaded is "default" in the sense that if you just use `#[tokio::main]` then you get a multi-threaded runtime but you can also just do `#[tokio::main(flavor = "current_thread")]` to get a single threaded executor.
Doing something extra to get a behavior different than default is the definition of opt-out my friend.
That argument doesn't hold up. Adding `#[tokio::main]` is opting in because it is that extra something that has to be done. Adding that line is opting in to the multithreaded runtime.
Doing something extra to get a behavior different than default is the definition of opt-out my friend.