Use cohttp-eio server

[yawaramin]

Getting results:

Node.js

$ wrk -d 10s http://127.0.0.1:8081/hi
Running 10s test @ http://127.0.0.1:8081/hi
  2 threads and 10 connections
  Thread Stats   Avg      Stdev     Max   +/- Stdev
    Latency   141.92us  448.18us  22.56ms   99.71%
    Req/Sec    39.15k     3.32k   44.56k    92.08%
  787003 requests in 10.10s, 126.09MB read
Requests/sec:  77923.26
Transfer/sec:     12.48MB

Cohttp-eio

$ wrk -d 10s http://127.0.0.1:8080/hi
Running 10s test @ http://127.0.0.1:8080/hi
  2 threads and 10 connections
  Thread Stats   Avg      Stdev     Max   +/- Stdev
    Latency    60.93us  144.59us   9.59ms   98.73%
    Req/Sec    81.82k     3.54k   87.49k    97.50%
  1627614 requests in 10.00s, 181.61MB read
Requests/sec: 162762.16
Transfer/sec:     18.16MB