jsonpb, why int64 to json is to string. like int64 str=10 -->str:"10" : 

//code:630
`
    //jsonpb, why int64 -> json is string. like 10-->"10"

    //https://github.com/golang/protobuf/blob/master/jsonpb/jsonpb.go

    // Default handling defers to the encoding/json library.
	b, err := json.Marshal(v.Interface())
	if err != nil {
		return err
	}
	needToQuote := string(b[0]) != `"` && (v.Kind() == reflect.Int64 || v.Kind() == reflect.Uint64)
	if needToQuote {
		out.write(`"`)
	}
	out.write(string(b))
	if needToQuote {
		out.write(`"`)
	}
`