warning: unused implementer of `futures::Future` that must be used
  --> src/main.rs:92:21
   |
92 |                     s.data(*channel, CryptoVec::from_slice(data));
   |                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = note: futures do nothing unless you `.await` or poll them
   = note: `#[warn(unused_must_use)]` on by default

Since 0.22+, .data method becomes async fn, but in the example code, it’s just not polled