otelhttp: Record metrics on timed out requests

CHANGELOG.md

@@ -15,6 +15,7 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 
 ### Fixed
 
+- Mimic the `context.WithoutCancel` behavior introduced in Go 1.21 to fix metric recording on timed out requests in `go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp`. (#4542)
 - Fix `NewServerHandler` in `go.opentelemetry.io/contrib/instrumentation/google.golang.org/grpc/otelgrpc` to correctly set the span status depending on the gRPC status. (#4587)
 - Update `go.opentelemetry.io/contrib/detectors/aws/ecs` to fix the task ARN when it is not valid. (#3583)
 - Do not panic in `go.opentelemetry.io/contrib/detectors/aws/ecs` when the container ARN is not valid. (#3583)

instrumentation/net/http/otelhttp/handler.go

@@ -284,33 +284,33 @@
 	})
 }
 
-func withoutCancel(ctx context.Context) context.Context {
-	if ctx.Done() == nil {
-		return ctx
+func withoutCancel(parent context.Context) context.Context {
+	if parent == nil {
+		panic("cannot create context from nil parent")
 	}
-	return withoutCancelCtx{ctx}
+	return withoutCancelCtx{parent}
 }
 
 type withoutCancelCtx struct {
 	c context.Context
 }
 
 func (withoutCancelCtx) Deadline() (deadline time.Time, ok bool) {
 	return
 }
 
 func (withoutCancelCtx) Done() <-chan struct{} {
 	return nil
 }
 
 func (withoutCancelCtx) Err() error {
 	return nil
 }
 
 func (w withoutCancelCtx) Value(key any) any {
 	return w.c.Value(key)
 }
 
 func (w withoutCancelCtx) String() string {
 	return "withoutCancel"
 }