async once tool for lazy_static

features:

• tokio
• async-std
• wasm-bindgen-futures

sample

```rust use lazystatic::lazystatic; use tokio::runtime::Runtime; // tokio feature use async_once::AsyncOnce;

lazy_static!{
    static ref FOO : AsyncOnce<u32> = AsyncOnce::new(async{
        1
    });
}
let mut rt = Runtime::new().unwrap();
rt.block_on(async {
    assert_eq!(FOO.get().await , 1)
})

```

run tests

cargo test --features tokio cargo test --features async-std wasm-pack test --node -- --features wasm-bindgen-futures