Implemented poll_flush for Box<S:Socket>

sqlx-core/src/net/socket/mod.rs

@@ -173,6 +173,10 @@
         (**self).poll_write_ready(cx)
     }
 
+    fn poll_flush(&mut self, cx: &mut Context<'_>) -> Poll<io::Result<()>> {
+        (**self).poll_flush(cx)
+    }
+
     fn poll_shutdown(&mut self, cx: &mut Context<'_>) -> Poll<io::Result<()>> {
         (**self).poll_shutdown(cx)
     }
@@ -222,8 +226,8 @@
 ///
 /// Returns an error if Unix Domain Sockets are not supported on this platform.
 pub async fn connect_uds<P: AsRef<Path>, Ws: WithSocket>(
     path: P,
     with_socket: Ws,
 ) -> crate::Result<Ws::Output> {
     #[cfg(not(unix))]
     {
@@ -254,7 +258,7 @@
     }
 
     #[cfg(not(feature = "_rt-async-std"))]
     {
         crate::rt::missing_rt((path, with_socket))
     }
 }