error: future cannot be sent between threads safely
 --> tests/debug_handler/fail/not_send.rs:3:1
  |
3 | #[debug_handler]
  | ^^^^^^^^^^^^^^^^ future returned by `handler` is not `Send`
  |
  = help: within `impl Future<Output = ()>`, the trait `Send` is not implemented for `Rc<()>`, which is required by `impl Future<Output = ()>: Send`
note: future is not `Send` as this value is used across an await
 --> tests/debug_handler/fail/not_send.rs:6:14
  |
5 |     let _rc = std::rc::Rc::new(());
  |         --- has type `Rc<()>` which is not `Send`
6 |     async {}.await;
  |              ^^^^^ await occurs here, with `_rc` maybe used later
note: required by a bound in `check`
 --> tests/debug_handler/fail/not_send.rs:3:1
  |
3 | #[debug_handler]
  | ^^^^^^^^^^^^^^^^ required by this bound in `check`
  = note: this error originates in the attribute macro `debug_handler` (in Nightly builds, run with -Z macro-backtrace for more info)