Replace async_trait with native RPITIT

Cargo.toml

@@ -14,7 +14,6 @@ publish = false
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
-async-trait = "0.1.77"
 aws-config = "1.1.1"
 aws-sdk-cloudfront = "1.9.0"
 aws-sdk-s3 = "1.11.0"

src/lib.rs

@@ -1,7 +1,6 @@
 mod s3;
 mod selfhosted;
 
-use async_trait::async_trait;
 use blake2::{Blake2b512, Digest};
 use flate2::read::GzDecoder;
 use log::{debug, info, trace};
@@ -12,6 +11,7 @@ use std::collections::HashMap;
 use std::error::Error;
 use std::fmt::{Debug, Display};
 use std::fs;
+use std::future::Future;
 use std::io::{Read, Seek};
 use std::path::Path;
 use std::path::PathBuf;
@@ -58,7 +58,6 @@ pub enum BuildEvent {
     Delete(String),
 }
 
-#[async_trait]
 pub trait Backend: Sized {
     // TODO: currently the get_options() methods are not actually called anywhere. It would be nice
     // if they were used in the CLI help output or BackendCreationErrors.
@@ -92,11 +91,11 @@ pub trait Backend: Sized {
     ///
     /// As there is the potential for race conditions when handling build events, backends must
     /// process any events with the same build ID serially in the order of their arrival.
-    async fn run(
+    fn run(
         &self,
         cache_dir: &Path,
-        mut rx: Receiver<BuildEvent>,
-    ) -> Result<(), Box<dyn std::error::Error>>;
+        rx: Receiver<BuildEvent>,
+    ) -> impl Future<Output = Result<(), Box<dyn std::error::Error>>> + Send;
 }
 
 /// Returns the checksum of an artifact tarball.

src/s3.rs

@@ -2,7 +2,6 @@ use crate::{
     get_cache_dir_checksum, to_filename_str, Backend, BackendCreationError, BuildEvent,
     CHECKSUM_FILENAME,
 };
-use async_trait::async_trait;
 use aws_config::BehaviorVersion;
 use aws_sdk_cloudfront::types::{InvalidationBatch, Paths};
 use aws_sdk_s3::primitives::ByteStream;
@@ -21,7 +20,6 @@ pub struct S3 {
     cloudfront_distribution: Option<String>,
 }
 
-#[async_trait]
 impl Backend for S3 {
     fn get_options() -> &'static [&'static str] {
         &["bucket", "path-prefix", "cloudfront-distribution"]

src/selfhosted.rs

@@ -1,5 +1,4 @@
 use crate::{Backend, BackendCreationError, BuildEvent};
-use async_trait::async_trait;
 use hyper::service::service_fn;
 use hyper::{Request, Response};
 use hyper_staticfile::{Body, Static};
@@ -56,7 +55,6 @@ async fn handle_request<B>(
     Ok(res)
 }
 
-#[async_trait]
 impl Backend for Selfhosted {
     fn get_options() -> &'static [&'static str] {
         &["address"]