Document ?Send

Author: dtolnay

README.md

@@ -127,6 +127,14 @@ impl Advertisement for AutoplayingVideo {
 
 <br>
 
+## Non-threadsafe futures
+
+Not all async traits need futures that are `dyn Future + Send`. To avoid having
+Send and Sync bounds placed on the async trait methods, invoke the async trait
+macro as `#[async_trait(?Send)]` on both the trait and the impl blocks.
+
+<br>
+
 ## Elided lifetimes
 
 Be aware that async fn syntax does not allow lifetime elision outside of `&` and

src/lib.rs

@@ -137,6 +137,15 @@
 //!
 //! <br><br>
 //!
+//! # Non-threadsafe futures
+//!
+//! Not all async traits need futures that are `dyn Future + Send`. To avoid
+//! having Send and Sync bounds placed on the async trait methods, invoke the
+//! async trait macro as `#[async_trait(?Send)]` on both the trait and the impl
+//! blocks.
+//!
+//! <br>
+//!
 //! # Elided lifetimes
 //!
 //! Be aware that async fn syntax does not allow lifetime elision outside of `&`