async-once-cell 0.1.0

Single assignment cells and lazy values.
Documentation 
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<p align="center"><img src="design/logo.png" alt="async_once_cell"></p>

[![Crates.io](https://img.shields.io/crates/v/async_once_cell.svg)](https://crates.io/crates/async_once_cell)
[![API reference](https://docs.rs/async_once_cell/badge.svg)](https://docs.rs/async_once_cell/)

# Overview

`async_once_cell` is a fork of [once_cell](https://crates.io/crates/once_cell)
that adds support for async initialization of cells. In a nutshell, API looks
*roughly* like this:

```rust
impl OnceCell<T> {
    fn new() -> OnceCell<T> { ... }
    fn set(&self, value: T) -> Result<(), T> { ... }
    fn get(&self) -> Option<&T> { ... }
}
```

Note that, like with `RefCell` and `Mutex`, the `set` method requires only a shared reference.
Because of the single assignment restriction `get` can return an `&T` instead of `Ref<T>`
or `MutexGuard<T>`.

`async_once_cell` also has a `Lazy<T>` type, build on top of `OnceCell` which provides the same API as
the `lazy_static!` macro, but without using any macros:

```rust
use std::{sync::Mutex, collections::HashMap};
use async_once_cell::sync::Lazy;

static GLOBAL_DATA: Lazy<Mutex<HashMap<i32, String>>> = Lazy::new(|| {
    let mut m = HashMap::new();
    m.insert(13, "Spica".to_string());
    m.insert(74, "Hoyten".to_string());
    Mutex::new(m)
});

fn main() {
    println!("{:?}", GLOBAL_DATA.lock().unwrap());
}
```

More patterns and use-cases are in the [docs](https://docs.rs/async_once_cell/)!

# Related crates

* [once_cell](https://crates.io/crates/once_cell)
* [double-checked-cell](https://github.com/niklasf/double-checked-cell)
* [lazy-init](https://crates.io/crates/lazy-init)
* [lazycell](https://crates.io/crates/lazycell)
* [mitochondria](https://crates.io/crates/mitochondria)
* [lazy_static](https://crates.io/crates/lazy_static)