[feature] replace encoding/json with jsoniter

**Is your feature request related to a problem? Please describe.**

no, just want to squeeze a bit of performance

**Describe the solution you'd like**.
> https://github.com/json-iterator/go

```
import jsoniter "github.com/json-iterator/go"

var json = jsoniter.ConfigCompatibleWithStandardLibrary
json.Unmarshal(input, &data)
```
