better feature detection

Author: dignifiedquire

src/transport/mod.rs

@@ -7,7 +7,7 @@ use std::{
     fmt::{self, Debug, Display},
     net::SocketAddr,
 };
-#[cfg(feature = "flume-transport")]
+#[cfg(all(feature = "flume-transport", feature = "tokio-mpsc-transport"))]
 pub mod boxed;
 #[cfg(feature = "combined-transport")]
 pub mod combined;