Fix timer channel drain to avoid hanging in Go 1.23 (#5869)

- Fix timer channel drain to avoid hanging in go1.23 w/ asynctimerchan=0
(#5868)

---------

Co-authored-by: Robert Pająk <[email protected]>
Co-authored-by: Damien Mathieu <[email protected]>

Author: 3 people

CHANGELOG.md

@@ -27,6 +27,7 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 
 - The race condition for multiple `FixedSize` exemplar reservoirs identified in #5814 is resolved. (#5819)
 - Fix log records duplication in case of heterogeneous resource attributes by correctly mapping each log record to it's resource and scope. (#5803)
+- Fix timer channel drain to avoid hanging on Go 1.23. (#5868)
 
 <!-- Released section -->
 <!-- Don't change this section unless doing release -->

sdk/trace/batch_span_processor.go

@@ -316,7 +316,11 @@ func (bsp *batchSpanProcessor) processQueue() {
 			bsp.batchMutex.Unlock()
 			if shouldExport {
 				if !bsp.timer.Stop() {
-					<-bsp.timer.C
+					// Handle both GODEBUG=asynctimerchan=[0|1] properly.
+					select {
+					case <-bsp.timer.C:
+					default:
+					}
 				}
 				if err := bsp.exportSpans(ctx); err != nil {
 					otel.Handle(err)