Incorrect marshalling of json.Number

[sudo-suhas]

Marshalling of json.Number values produces incorrect result:

package main

import (
	"encoding/json"
	"fmt"

	jsoniter "github.com/json-iterator/go"
)

type Nums struct {
	N1 json.Number `json:"n1,Number"`
	N2 json.Number `json:"n2,Number"`
}

func check(err error) {
	if err != nil {
		panic(err)
	}
}

func main() {
	data := []byte(`{ "n1": 1.2, "n2": "" }`)

	var v1 Nums
	check(json.Unmarshal(data, &v1))
	bs, err := json.Marshal(v1)
	check(err)
	fmt.Printf("\nWith standard library:\n\tValue: %#v\n\tMarshalled: %s\n", v1, bs)

	var v2 Nums
	check(jsoniter.Unmarshal(data, &v2))
	bs, err = jsoniter.Marshal(v2)
	check(err)
	fmt.Printf("\nWith jsoniter:\n\tValue: %#v\n\tMarshalled: %s\n", v2, bs)

	custJSON := jsoniter.Config{
		UseNumber:               true,
		EscapeHTML:              false,
		MarshalFloatWith6Digits: true,
	}.Froze()
	var v3 Nums
	check(custJSON.Unmarshal(data, &v3))
	bs, err = custJSON.Marshal(v3)
	check(err)
	fmt.Printf("\nWith jsoniter custom config:\n\tValue: %#v\n\tMarshalled: %s\n", v3, bs)
	check(jsoniter.Unmarshal(bs, &v2))
}

Output:

With standard library:
	Value: main.Nums{N1:"1.2", N2:""}
	Marshalled: {"n1":1.2,"n2":0}

With jsoniter:
	Value: main.Nums{N1:"1.2", N2:""}
	Marshalled: {"n1":1.2,"n2":}

With jsoniter custom config:
	Value: main.Nums{N1:"1.2", N2:""}
	Marshalled: {"n1":1.2,"n2":}
panic: main.Nums: N2: readNumberAsString: invalid number, error found in #10 byte of ...|:1.2,"n2":}|..., bigger context ...|{"n1":1.2,"n2":}|...

goroutine 1 [running]:
main.check(0x5e43c0, 0xc042044600)
	e:/workspace/golang/src/playground/jsoniter_num.go:17 +0x51
main.main()
	e:/workspace/golang/src/playground/jsoniter_num.go:46 +0x808
exit status 2

[sudo-suhas]

Thanks for the quick fix @taowen! Could you please also make a release for this?