A generic async ACME create.
The main goal is to allow binaries to choose what async runtime and TLS lib is used.
You need to specify via features what crates are used to the actual work.
|feature flag|Meaning|
|---|---|
|usetokio | Use tokio as async runtime|
|useasyncstd | Use asyncstd as async runtime|
|userustls | Use rustls for HTTPS and generate Certificates tailored to it|
|hyperrustls | use_rustls+use_tokio 
use_rustls+use_async_std 
Without anything specified you will end up with no async backend selected or no crypto backend selected. If you use this crate for a library, please reexport the apropriate features.
Rust offers different async runtimes that - on a high level - offer the same thing: asyncrounes functions for files, sockets and so on.
So if you write a lib and need some basic stiff (like an http client) you sometimes have to make choices that are not what your crates users would have liked. For example: I wrote a webserver based on hyper and wanted to add ACME. A crate I found did what I needed but used async-h1 and async-std. While that worked, it did increase the binary size and crates I depend on by a good amount.
So I wrote this. You can specify which backend to use.
In the Webserver case, using --features="hyper_rustls" (same dependencies) instead of --features="async_std_rustls" did lead to 81 less crates and a 350kB smaller binary.
Using:
[profile.release]
lto = "fat"
codegen-units = 1
These query certs from Let's Encrypts Staging endpoint.
In order for them to work you need to change the email and domain from example.com to your own.
cargo run --example hyper_rustls --features="hyper_rustls"cargo run --example async_rustls --features="async_std_rustls"