Add Experimental HTTP/3 Support (#1599)

This adds experimental HTTP/3 support, using `h3` and `h3-quinn` (though the internals are not to be depended on).

.gitignore

@@ -1,3 +1,4 @@
 target
 Cargo.lock
 *.swp
+.idea

Cargo.toml

@@ -62,6 +62,9 @@ stream = ["tokio/fs", "tokio-util", "wasm-streams"]
 
 socks = ["tokio-socks"]
 
+# Experimental HTTP/3 client.
+http3 = ["rustls-tls", "h3", "h3-quinn", "quinn", "futures-channel"]
+
 # Internal (PRIVATE!) features used to aid testing.
 # Don't rely on these whatsoever. They may disappear at anytime.
 
@@ -135,6 +138,13 @@ tokio-socks = { version = "0.5.1", optional = true }
 ## trust-dns
 trust-dns-resolver = { version = "0.22", optional = true }
 
+# HTTP/3 experimental support
+h3 = { version="0.0.1", optional = true }
+h3-quinn = { version="0.0.1", optional = true }
+quinn = { version = "0.8", default-features = false, features = ["tls-rustls", "ring"], optional = true  }
+futures-channel = { version="0.3", optional = true}
+
+
 [target.'cfg(not(target_arch = "wasm32"))'.dev-dependencies]
 env_logger = "0.8"
 hyper = { version = "0.14", default-features = false, features = ["tcp", "stream", "http1", "http2", "client", "server", "runtime"] }

examples/h3_simple.rs

@@ -0,0 +1,51 @@
+#![deny(warnings)]
+
+// This is using the `tokio` runtime. You'll need the following dependency:
+//
+// `tokio = { version = "1", features = ["full"] }`
+#[cfg(feature = "http3")]
+#[cfg(not(target_arch = "wasm32"))]
+#[tokio::main]
+async fn main() -> Result<(), reqwest::Error> {
+    use http::Version;
+    use reqwest::{Client, IntoUrl, Response};
+
+    async fn get<T: IntoUrl + Clone>(url: T) -> reqwest::Result<Response> {
+        Client::builder()
+            .http3_prior_knowledge()
+            .build()?
+            .get(url)
+            .version(Version::HTTP_3)
+            .send()
+            .await
+    }
+
+    // Some simple CLI args requirements...
+    let url = match std::env::args().nth(1) {
+        Some(url) => url,
+        None => {
+            println!("No CLI URL provided, using default.");
+            "https://hyper.rs".into()
+        }
+    };
+
+    eprintln!("Fetching {:?}...", url);
+
+    let res = get(url).await?;
+
+    eprintln!("Response: {:?} {}", res.version(), res.status());
+    eprintln!("Headers: {:#?}\n", res.headers());
+
+    let body = res.text().await?;
+
+    println!("{}", body);
+
+    Ok(())
+}
+
+// The [cfg(not(target_arch = "wasm32"))] above prevent building the tokio::main function
+// for wasm32 target, because tokio isn't compatible with wasm32.
+// If you aren't building for wasm32, you don't need that line.
+// The two lines below avoid the "'main' function not found" error when building for wasm32 target.
+#[cfg(any(target_arch = "wasm32", not(feature = "http3")))]
+fn main() {}