Attempts to retrieve the global state for type T.

Returns Some if the state has previously been set. Otherwise returns None.

Example

use std::sync::atomic::{AtomicUsize, Ordering};

struct MyState(AtomicUsize);

// State for `T` is initially unset.
assert!(state::try_get::<MyState>().is_none());

state::set(MyState(AtomicUsize::new(0)));

let my_state = state::try_get::<MyState>().expect("MyState");
assert_eq!(my_state.0.load(Ordering::Relaxed), 0);