track task spawn location for tokio instrumentation (#1201)

Author: hds

src/runtime.rs

@@ -54,6 +54,7 @@ pub(crate) use tls::TlsConfig;
 ///
 /// This must be called from an async block
 /// or function running on a runtime.
+#[track_caller]
 pub(crate) fn spawn<F, O>(fut: F) -> AsyncJoinHandle<O>
 where
     F: Future<Output = O> + Send + 'static,

src/runtime/join_handle.rs

@@ -9,6 +9,7 @@ use std::{
 pub(crate) struct AsyncJoinHandle<T>(tokio::task::JoinHandle<T>);
 
 impl<T> AsyncJoinHandle<T> {
+    #[track_caller]
     pub(crate) fn spawn<F>(fut: F) -> Self
     where
         F: Future<Output = T> + Send + 'static,