Add GODEBUG=asynctimerchan=0 to CI for Go 1.25 synctest compatibility

Author: sasha-s

.github/workflows/go.yml

@@ -31,3 +31,5 @@ jobs:
 
       - name: Test
         run: go test -v -bench=. -coverprofile=coverage.txt ./...
+        env:
+          GODEBUG: asynctimerchan=0