feat(lib): Upgrade to Tokio 1.0 (#2369)

Closes #2370

src/client/connect/http.rs

@@ -667,8 +667,11 @@ impl ConnectingTcp<'_> {
                 let fallback_fut = fallback.remote.connect(self.config);
                 futures_util::pin_mut!(fallback_fut);
 
+                let fallback_delay = fallback.delay;
+                futures_util::pin_mut!(fallback_delay);
+
                 let (result, future) =
-                    match futures_util::future::select(preferred_fut, fallback.delay).await {
+                    match futures_util::future::select(preferred_fut, fallback_delay).await {
                         Either::Left((result, _fallback_delay)) => {
                             (result, Either::Right(fallback_fut))
                         }

src/client/dispatch.rs

@@ -1,7 +1,7 @@
 #[cfg(feature = "http2")]
 use std::future::Future;
 
-use tokio::stream::Stream;
+use futures_util::FutureExt;
 use tokio::sync::{mpsc, oneshot};
 
 use crate::common::{task, Pin, Poll};
@@ -150,8 +150,8 @@ impl<T, U> Receiver<T, U> {
         self: Pin<&mut Self>,
         cx: &mut task::Context<'_>,
     ) -> Poll<Option<(T, Callback<T, U>)>> {
-        let this = self.project();
-        match this.inner.poll_next(cx) {
+        let mut this = self.project();
+        match this.inner.poll_recv(cx) {
             Poll::Ready(item) => {
                 Poll::Ready(item.map(|mut env| env.0.take().expect("envelope not dropped")))
             }
@@ -170,9 +170,9 @@ impl<T, U> Receiver<T, U> {
 
     #[cfg(feature = "http1")]
     pub(crate) fn try_recv(&mut self) -> Option<(T, Callback<T, U>)> {
-        match self.inner.try_recv() {
-            Ok(mut env) => env.0.take(),
-            Err(_) => None,
+        match self.inner.recv().now_or_never() {
+            Some(Some(mut env)) => env.0.take(),
+            _ => None,
         }
     }
 }

src/client/pool.rs

@@ -731,7 +731,6 @@ impl<T: Poolable + 'static> Future for IdleTask<T> {
     type Output = ();
 
     fn poll(self: Pin<&mut Self>, cx: &mut task::Context<'_>) -> Poll<Self::Output> {
-        use tokio::stream::Stream;
         let mut this = self.project();
         loop {
             match this.pool_drop_notifier.as_mut().poll(cx) {
@@ -743,7 +742,7 @@ impl<T: Poolable + 'static> Future for IdleTask<T> {
                 }
             }
 
-            ready!(this.interval.as_mut().poll_next(cx));
+            ready!(this.interval.as_mut().poll_tick(cx));
 
             if let Some(inner) = this.pool.upgrade() {
                 if let Ok(mut inner) = inner.lock() {