Fix example-unix-domain-socket on non-unix platforms (#919)

* remove unused `axum`'s dependency:`tokio-util`

* fix `examples/todos`'s `async fn todos_index` iter_overeager_cloned

* Add docs to `/examples/async-graphql`, just like other xamples.

* remove `examples/async-graphql` unused dependencies `tracing-subscriber` and `trace`

* `examples/chat` deps `trace` and `tracing-subscriber` never be used. Add trace `debug` to `chat`

* remove `examples/print-request-response` unused dependency `axum-extra`

* remove `examples/prometheus-metrics` unused dependency `axum-extra`

* remove `examples/reverse-proxy` unused dependencies `tracing-subscriber` and `trace`

* `examples/chat` fmt fix

* fix `example-unix-domain-socket` compile error on not-unix platforms

Co-authored-by: zys864 <zys864@qq.com>
Co-authored-by: zys864 <zys864@gmail.com>

examples/unix-domain-socket/src/main.rs

@@ -4,6 +4,19 @@
 //! cargo run -p example-unix-domain-socket
 //! ```
 
+#[cfg(unix)]
+#[tokio::main]
+async fn main() {
+    unix::server().await;
+}
+
+#[cfg(not(unix))]
+fn main() {
+    println!("This example requires unix")
+}
+
+#[cfg(unix)]
+mod unix {
     use axum::{
         body::Body,
         extract::connect_info::{self, ConnectInfo},
@@ -30,14 +43,7 @@ use tokio::{
     use tower::BoxError;
     use tracing_subscriber::{layer::SubscriberExt, util::SubscriberInitExt};
 
-#[cfg(not(unix))]
-fn main() {
-    println!("This example requires unix")
-}
-
-#[cfg(unix)]
-#[tokio::main]
-async fn main() {
+    pub async fn server() {
         tracing_subscriber::registry()
             .with(tracing_subscriber::EnvFilter::new(
                 std::env::var("RUST_LOG").unwrap_or_else(|_| "debug".into()),
@@ -122,7 +128,10 @@ impl AsyncWrite for ClientConnection {
             Pin::new(&mut self.stream).poll_write(cx, buf)
         }
 
-    fn poll_flush(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<(), io::Error>> {
+        fn poll_flush(
+            mut self: Pin<&mut Self>,
+            cx: &mut Context<'_>,
+        ) -> Poll<Result<(), io::Error>> {
             Pin::new(&mut self.stream).poll_flush(cx)
         }
 
@@ -168,3 +177,4 @@ impl connect_info::Connected<&UnixStream> for UdsConnectInfo {
             }
         }
     }
+}