DelayQueue

``` bash $ cargo test -- --nocapture

Response Latency Count Percent 100 7 0.70% 200 81 8.10% 300 115 11.50% 400 201 20.10% 500 316 31.60% 600 99 9.90% 1000 181 18.10% test test::test ... ok

test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 9.99s ```