diff --git a/vendor/github.com/json-iterator/go/reflect_optional.go b/vendor/github.com/json-iterator/go/reflect_optional.go
new file mode 100644
index 0000000..43ec71d
--- /dev/null
+++ b/vendor/github.com/json-iterator/go/reflect_optional.go
@@ -0,0 +1,133 @@
+package jsoniter
+
+import (
+	"github.com/modern-go/reflect2"
+	"reflect"
+	"unsafe"
+)
+
+func decoderOfOptional(ctx *ctx, typ reflect2.Type) ValDecoder {
+	ptrType := typ.(*reflect2.UnsafePtrType)
+	elemType := ptrType.Elem()
+	decoder := decoderOfType(ctx, elemType)
+	if ctx.prefix == "" && elemType.Kind() == reflect.Ptr {
+		return &dereferenceDecoder{elemType, decoder}
+	}
+	return &OptionalDecoder{elemType, decoder}
+}
+
+func encoderOfOptional(ctx *ctx, typ reflect2.Type) ValEncoder {
+	ptrType := typ.(*reflect2.UnsafePtrType)
+	elemType := ptrType.Elem()
+	elemEncoder := encoderOfType(ctx, elemType)
+	encoder := &OptionalEncoder{elemEncoder}
+	return encoder
+}
+
+type OptionalDecoder struct {
+	ValueType    reflect2.Type
+	ValueDecoder ValDecoder
+}
+
+func (decoder *OptionalDecoder) Decode(ptr unsafe.Pointer, iter *Iterator) {
+	if iter.ReadNil() {
+		*((*unsafe.Pointer)(ptr)) = nil
+	} else {
+		if *((*unsafe.Pointer)(ptr)) == nil {
+			//pointer to null, we have to allocate memory to hold the value
+			newPtr := decoder.ValueType.UnsafeNew()
+			decoder.ValueDecoder.Decode(newPtr, iter)
+			*((*unsafe.Pointer)(ptr)) = newPtr
+		} else {
+			//reuse existing instance
+			decoder.ValueDecoder.Decode(*((*unsafe.Pointer)(ptr)), iter)
+		}
+	}
+}
+
+type dereferenceDecoder struct {
+	// only to deference a pointer
+	valueType    reflect2.Type
+	valueDecoder ValDecoder
+}
+
+func (decoder *dereferenceDecoder) Decode(ptr unsafe.Pointer, iter *Iterator) {
+	if *((*unsafe.Pointer)(ptr)) == nil {
+		//pointer to null, we have to allocate memory to hold the value
+		newPtr := decoder.valueType.UnsafeNew()
+		decoder.valueDecoder.Decode(newPtr, iter)
+		*((*unsafe.Pointer)(ptr)) = newPtr
+	} else {
+		//reuse existing instance
+		decoder.valueDecoder.Decode(*((*unsafe.Pointer)(ptr)), iter)
+	}
+}
+
+type OptionalEncoder struct {
+	ValueEncoder ValEncoder
+}
+
+func (encoder *OptionalEncoder) Encode(ptr unsafe.Pointer, stream *Stream) {
+	if *((*unsafe.Pointer)(ptr)) == nil {
+		stream.WriteNil()
+	} else {
+		encoder.ValueEncoder.Encode(*((*unsafe.Pointer)(ptr)), stream)
+	}
+}
+
+func (encoder *OptionalEncoder) IsEmpty(ptr unsafe.Pointer) bool {
+	return *((*unsafe.Pointer)(ptr)) == nil
+}
+
+type dereferenceEncoder struct {
+	ValueEncoder ValEncoder
+}
+
+func (encoder *dereferenceEncoder) Encode(ptr unsafe.Pointer, stream *Stream) {
+	if *((*unsafe.Pointer)(ptr)) == nil {
+		stream.WriteNil()
+	} else {
+		encoder.ValueEncoder.Encode(*((*unsafe.Pointer)(ptr)), stream)
+	}
+}
+
+func (encoder *dereferenceEncoder) IsEmpty(ptr unsafe.Pointer) bool {
+	dePtr := *((*unsafe.Pointer)(ptr))
+	if dePtr == nil {
+		return true
+	}
+	return encoder.ValueEncoder.IsEmpty(dePtr)
+}
+
+func (encoder *dereferenceEncoder) IsEmbeddedPtrNil(ptr unsafe.Pointer) bool {
+	deReferenced := *((*unsafe.Pointer)(ptr))
+	if deReferenced == nil {
+		return true
+	}
+	isEmbeddedPtrNil, converted := encoder.ValueEncoder.(IsEmbeddedPtrNil)
+	if !converted {
+		return false
+	}
+	fieldPtr := unsafe.Pointer(deReferenced)
+	return isEmbeddedPtrNil.IsEmbeddedPtrNil(fieldPtr)
+}
+
+type referenceEncoder struct {
+	encoder ValEncoder
+}
+
+func (encoder *referenceEncoder) Encode(ptr unsafe.Pointer, stream *Stream) {
+	encoder.encoder.Encode(unsafe.Pointer(&ptr), stream)
+}
+
+func (encoder *referenceEncoder) IsEmpty(ptr unsafe.Pointer) bool {
+	return encoder.encoder.IsEmpty(unsafe.Pointer(&ptr))
+}
+
+type referenceDecoder struct {
+	decoder ValDecoder
+}
+
+func (decoder *referenceDecoder) Decode(ptr unsafe.Pointer, iter *Iterator) {
+	decoder.decoder.Decode(unsafe.Pointer(&ptr), iter)
+}