improve performance by reduce hiddin class on every request

Before: qps 2569.09, rt 5.46ms
After : qps 3565.10, rt 2.79ms

## Before

```bash
$ wrk -d 10 -t 10 -c 10 http://localhost:3000/
Running 10s test @ http://localhost:3000/
  10 threads and 10 connections
  Thread Stats   Avg      Stdev     Max   +/- Stdev
    Latency     5.46ms    7.76ms  54.76ms   94.40%
    Req/Sec   270.33     83.57   500.00     74.67%
  25693 requests in 10.00s, 7.23MB read
Requests/sec:   2569.09
Transfer/sec:    740.12KB
```

## After

```bash
$ wrk -d 10 -t 10 -c 10 http://localhost:3000/
Running 10s test @ http://localhost:3000/
  10 threads and 10 connections
  Thread Stats   Avg      Stdev     Max   +/- Stdev
    Latency     2.79ms  652.20us  14.25ms   91.25%
    Req/Sec   381.62     66.41   666.00     72.18%
  35651 requests in 10.00s, 10.03MB read
Requests/sec:   3565.10
Transfer/sec:      1.00MB
```
no need for `.npmignore` when we use `.files` in `package.json`