refactor all to async/await (#617)

Co-authored-by: Danny Browning <danny.browning@protectwise.com>
Co-authored-by: Daniel Eades <danieleades@hotmail.com>

examples/async_multiple_requests.rs

@@ -1,8 +1,8 @@
 #![deny(warnings)]
 
-use futures::Future;
 use reqwest::r#async::{Client, Response};
 use serde::Deserialize;
+use std::future::Future;
 
 #[derive(Deserialize, Debug)]
 struct Slideshow {
@@ -15,26 +15,27 @@ struct SlideshowContainer {
     slideshow: Slideshow,
 }
 
-fn fetch() -> impl Future<Item = (), Error = ()> {
+async fn into_json<F>(f: F) -> Result<SlideshowContainer, reqwest::Error>
+where
+    F: Future<Output = Result<Response, reqwest::Error>>,
+{
+    let mut resp = f.await?;
+    resp.json::<SlideshowContainer>().await
+}
+
+#[tokio::main]
+async fn main() -> Result<(), reqwest::Error> {
     let client = Client::new();
 
-    let json = |mut res: Response| res.json::<SlideshowContainer>();
+    let request1 = client.get("https://httpbin.org/json").send();
 
-    let request1 = client.get("https://httpbin.org/json").send().and_then(json);
+    let request2 = client.get("https://httpbin.org/json").send();
 
-    let request2 = client.get("https://httpbin.org/json").send().and_then(json);
+    let (try_json1, try_json2) =
+        futures::future::join(into_json(request1), into_json(request2)).await;
 
-    request1
-        .join(request2)
-        .map(|(res1, res2)| {
-            println!("{:?}", res1);
-            println!("{:?}", res2);
-        })
-        .map_err(|err| {
-            println!("stdout error: {}", err);
-        })
-}
-
-fn main() {
-    tokio::run(fetch());
+    println!("{:?}", try_json1?);
+    println!("{:?}", try_json2?);
+
+    Ok(())
 }