Vendor dependencies

Let's see how I like this workflow.

vendor/tokio/tests/tcp_echo.rs

@@ -0,0 +1,42 @@
+#![warn(rust_2018_idioms)]
+#![cfg(all(feature = "full", not(tokio_wasi)))] // Wasi doesn't support bind
+
+use tokio::io::{self, AsyncReadExt, AsyncWriteExt};
+use tokio::net::{TcpListener, TcpStream};
+use tokio::sync::oneshot;
+use tokio_test::assert_ok;
+
+#[tokio::test]
+async fn echo_server() {
+    const ITER: usize = 1024;
+
+    let (tx, rx) = oneshot::channel();
+
+    let srv = assert_ok!(TcpListener::bind("127.0.0.1:0").await);
+    let addr = assert_ok!(srv.local_addr());
+
+    let msg = "foo bar baz";
+    tokio::spawn(async move {
+        let mut stream = assert_ok!(TcpStream::connect(&addr).await);
+
+        for _ in 0..ITER {
+            // write
+            assert_ok!(stream.write_all(msg.as_bytes()).await);
+
+            // read
+            let mut buf = [0; 11];
+            assert_ok!(stream.read_exact(&mut buf).await);
+            assert_eq!(&buf[..], msg.as_bytes());
+        }
+
+        assert_ok!(tx.send(()));
+    });
+
+    let (mut stream, _) = assert_ok!(srv.accept().await);
+    let (mut rd, mut wr) = stream.split();
+
+    let n = assert_ok!(io::copy(&mut rd, &mut wr).await);
+    assert_eq!(n, (ITER * msg.len()) as u64);
+
+    assert_ok!(rx.await);
+}