fix(tracing): propagate span context

The tracing span context set in consumers of the `TokioExecutor` was
sometimes lost (if the task was run in a different thread). This adds a
call to `in_current_span()` to preserve it.

Author: alpeb

Cargo.toml

@@ -69,7 +69,7 @@ service = ["dep:tower-service"]
 http1 = ["hyper/http1"]
 http2 = ["hyper/http2"]
 
-tokio = ["dep:tokio", "tokio/net", "tokio/rt", "tokio/time"]
+tokio = ["dep:tokio", "tokio/net", "tokio/rt", "tokio/time", "dep:tracing"]
 
 # internal features used in CI
 __internal_happy_eyeballs_tests = []

src/rt/tokio.rs

@@ -9,6 +9,7 @@ use std::{
 
 use hyper::rt::{Executor, Sleep, Timer};
 use pin_project_lite::pin_project;
+use tracing::instrument::Instrument;
 
 /// Future executor that utilises `tokio` threads.
 #[non_exhaustive]
@@ -49,7 +50,7 @@ where
     Fut::Output: Send + 'static,
 {
     fn execute(&self, fut: Fut) {
-        tokio::spawn(fut);
+        tokio::spawn(fut.in_current_span());
     }
 }