Propagate cancelled request

[xlc]

Run a Subway, disable internet (i.e turn wifi off), curl request /liveness, ctrl+c it, enable internet, see warning Failed to send response

This is most likely due to that cancel the request from user does not cancel the outgoing request to upstream and then later it tries to send response back and the receiver is already dropped.

Need a way to ensure cancelled request will result the upstream request also get cancelled

subway/src/extensions/client/mod.rs

Line 170 in 65e9de3

tracing::debug!("Request failed: {:?}", err);