func (iter *Iterator) ReadVal(obj interface{}) {
	cacheKey := reflect2.RTypeOf(obj)
	decoder := iter.cfg.getDecoderFromCache(cacheKey)
	if decoder == nil {
		typ := reflect2.TypeOf(obj)
		if typ.Kind() != reflect.Ptr {
			iter.ReportError("ReadVal", "can only unmarshal into pointer")
			return
		}
		decoder = iter.cfg.DecoderOf(typ)
	}
	ptr := reflect2.PtrOf(obj)
	if ptr == nil {
		iter.ReportError("ReadVal", "can not read into nil pointer")
		return
	}
	decoder.Decode(ptr, iter)
}
ReadVal copy the underlying JSON into go interface, same as json.Unmarshal
package jsoniter
import (
	"fmt"
	"reflect"
	"unsafe"
	"github.com/modern-go/reflect2"
)
type ValDecoder interface {
	Decode(ptr unsafe.Pointer, iter *Iterator)
}
type ValEncoder interface {
	IsEmpty(ptr unsafe.Pointer) bool
	Encode(ptr unsafe.Pointer, stream *Stream)
}
type checkIsEmpty interface {
	IsEmpty(ptr unsafe.Pointer) bool
}
type ctx struct {
	*frozenConfig
	prefix   string
	encoders map[reflect2.Type]ValEncoder
	decoders map[reflect2.Type]ValDecoder
}
func (b *ctx) caseSensitive() bool {
	if b.frozenConfig == nil {
		return false
	}
	return b.frozenConfig.caseSensitive
}
func (b *ctx) append(prefix string) *ctx {
	return &ctx{
		frozenConfig: b.frozenConfig,
		prefix:       b.prefix + " " + prefix,
		encoders:     b.encoders,
		decoders:     b.decoders,
	}
}