That comes from the where the tokio task is spawned annotating the future with send. https://docs.rs/tokio/latest/tokio/task/fn.spawn.html https://docs.rs/toki

That comes from the where the tokio task is spawned annotating the future with send. https://docs.rs/tokio/latest/tokio/task/fn.spawn.html https://docs.rs/tokio/latest/tokio/task/fn.spawn.html If you want to run everything on the same thread then localset enables that. See how the spawn function does not include the send bound. https://docs.rs/tokio/latest/tokio/task/struct.LocalSet.html https://docs.rs/tokio/latest/tokio/task/struct.LocalSet.html