Use a pool of rand.Source to reduce lock contention when creating span ids (#357)
Use a pool of rand.Source to reduce lock contention when creating span ids (#357)

Signed-off-by: Gary Brown <f9023000f29773649f3850298becb9544b5fd6a9@brownuk.com>
uber/jaeger-client-go,uber/jaeger-client-go,uber/jaeger-client-go