Fix threading by carrying forward span reference in use_scope
#221
| Job | Run time |
|---|---|
| 2m 5s | |
| 2m 5s | |
| 5m 8s | |
| 5m 8s | |
| 3m 11s | |
| 3m 11s | |
| 3m 1s | |
| 3m 6s | |
| 4m 34s | |
| 4m 34s | |
| 3m 6s | |
| 3m 6s | |
| 5m 16s | |
| 5m 16s | |
| 4m 7s | |
| 4m 7s | |
| 6m 15s | |
| 6m 15s | |
| 7m 27s | |
| 7m 27s | |
| 1s | |
| 1s | |
| 1h 28m 27s |