alt Hacker NewsEverything is not async in Go.
If your threads are "free" you can just run 400 copies of a synchronous code and blocking in one just frees the thread to work on other. async within same goroutine is still very much opt in (you have to manually create goroutine that writes to channel that you then receive on), it just isn't needed where "spawn a thread for each connecton" costs you barely few kb per connection.
What GP meant - what everyone means when they say this - is that goroutines are always M:N threading and so there is no such thing as function coloring. In Rust to get M:N threading you have to use async and in practice every library you use has to use async. Hence function coloring, and two separate ecosystems of libraries in the same language.