diff --git a/vendor/github.com/modern-go/reflect2/unsafe_slice.go b/vendor/github.com/modern-go/reflect2/unsafe_slice.go
new file mode 100644
index 0000000..1c6d876
--- /dev/null
+++ b/vendor/github.com/modern-go/reflect2/unsafe_slice.go
@@ -0,0 +1,177 @@
+package reflect2
+
+import (
+	"reflect"
+	"unsafe"
+)
+
+// sliceHeader is a safe version of SliceHeader used within this package.
+type sliceHeader struct {
+	Data unsafe.Pointer
+	Len  int
+	Cap  int
+}
+
+type UnsafeSliceType struct {
+	unsafeType
+	elemRType  unsafe.Pointer
+	pElemRType unsafe.Pointer
+	elemSize   uintptr
+}
+
+func newUnsafeSliceType(cfg *frozenConfig, type1 reflect.Type) SliceType {
+	elemType := type1.Elem()
+	return &UnsafeSliceType{
+		unsafeType: *newUnsafeType(cfg, type1),
+		pElemRType: unpackEFace(reflect.PtrTo(elemType)).data,
+		elemRType:  unpackEFace(elemType).data,
+		elemSize:   elemType.Size(),
+	}
+}
+
+func (type2 *UnsafeSliceType) Set(obj interface{}, val interface{}) {
+	objEFace := unpackEFace(obj)
+	assertType("Type.Set argument 1", type2.ptrRType, objEFace.rtype)
+	valEFace := unpackEFace(val)
+	assertType("Type.Set argument 2", type2.ptrRType, valEFace.rtype)
+	type2.UnsafeSet(objEFace.data, valEFace.data)
+}
+
+func (type2 *UnsafeSliceType) UnsafeSet(ptr unsafe.Pointer, val unsafe.Pointer) {
+	*(*sliceHeader)(ptr) = *(*sliceHeader)(val)
+}
+
+func (type2 *UnsafeSliceType) IsNil(obj interface{}) bool {
+	if obj == nil {
+		return true
+	}
+	objEFace := unpackEFace(obj)
+	assertType("Type.IsNil argument 1", type2.ptrRType, objEFace.rtype)
+	return type2.UnsafeIsNil(objEFace.data)
+}
+
+func (type2 *UnsafeSliceType) UnsafeIsNil(ptr unsafe.Pointer) bool {
+	if ptr == nil {
+		return true
+	}
+	return (*sliceHeader)(ptr).Data == nil
+}
+
+func (type2 *UnsafeSliceType) SetNil(obj interface{}) {
+	objEFace := unpackEFace(obj)
+	assertType("SliceType.SetNil argument 1", type2.ptrRType, objEFace.rtype)
+	type2.UnsafeSetNil(objEFace.data)
+}
+
+func (type2 *UnsafeSliceType) UnsafeSetNil(ptr unsafe.Pointer) {
+	header := (*sliceHeader)(ptr)
+	header.Len = 0
+	header.Cap = 0
+	header.Data = nil
+}
+
+func (type2 *UnsafeSliceType) MakeSlice(length int, cap int) interface{} {
+	return packEFace(type2.ptrRType, type2.UnsafeMakeSlice(length, cap))
+}
+
+func (type2 *UnsafeSliceType) UnsafeMakeSlice(length int, cap int) unsafe.Pointer {
+	header := &sliceHeader{unsafe_NewArray(type2.elemRType, cap), length, cap}
+	return unsafe.Pointer(header)
+}
+
+func (type2 *UnsafeSliceType) LengthOf(obj interface{}) int {
+	objEFace := unpackEFace(obj)
+	assertType("SliceType.Len argument 1", type2.ptrRType, objEFace.rtype)
+	return type2.UnsafeLengthOf(objEFace.data)
+}
+
+func (type2 *UnsafeSliceType) UnsafeLengthOf(obj unsafe.Pointer) int {
+	header := (*sliceHeader)(obj)
+	return header.Len
+}
+
+func (type2 *UnsafeSliceType) SetIndex(obj interface{}, index int, elem interface{}) {
+	objEFace := unpackEFace(obj)
+	assertType("SliceType.SetIndex argument 1", type2.ptrRType, objEFace.rtype)
+	elemEFace := unpackEFace(elem)
+	assertType("SliceType.SetIndex argument 3", type2.pElemRType, elemEFace.rtype)
+	type2.UnsafeSetIndex(objEFace.data, index, elemEFace.data)
+}
+
+func (type2 *UnsafeSliceType) UnsafeSetIndex(obj unsafe.Pointer, index int, elem unsafe.Pointer) {
+	header := (*sliceHeader)(obj)
+	elemPtr := arrayAt(header.Data, index, type2.elemSize, "i < s.Len")
+	typedmemmove(type2.elemRType, elemPtr, elem)
+}
+
+func (type2 *UnsafeSliceType) GetIndex(obj interface{}, index int) interface{} {
+	objEFace := unpackEFace(obj)
+	assertType("SliceType.GetIndex argument 1", type2.ptrRType, objEFace.rtype)
+	elemPtr := type2.UnsafeGetIndex(objEFace.data, index)
+	return packEFace(type2.pElemRType, elemPtr)
+}
+
+func (type2 *UnsafeSliceType) UnsafeGetIndex(obj unsafe.Pointer, index int) unsafe.Pointer {
+	header := (*sliceHeader)(obj)
+	return arrayAt(header.Data, index, type2.elemSize, "i < s.Len")
+}
+
+func (type2 *UnsafeSliceType) Append(obj interface{}, elem interface{}) {
+	objEFace := unpackEFace(obj)
+	assertType("SliceType.Append argument 1", type2.ptrRType, objEFace.rtype)
+	elemEFace := unpackEFace(elem)
+	assertType("SliceType.Append argument 2", type2.pElemRType, elemEFace.rtype)
+	type2.UnsafeAppend(objEFace.data, elemEFace.data)
+}
+
+func (type2 *UnsafeSliceType) UnsafeAppend(obj unsafe.Pointer, elem unsafe.Pointer) {
+	header := (*sliceHeader)(obj)
+	oldLen := header.Len
+	type2.UnsafeGrow(obj, oldLen+1)
+	type2.UnsafeSetIndex(obj, oldLen, elem)
+}
+
+func (type2 *UnsafeSliceType) Cap(obj interface{}) int {
+	objEFace := unpackEFace(obj)
+	assertType("SliceType.Cap argument 1", type2.ptrRType, objEFace.rtype)
+	return type2.UnsafeCap(objEFace.data)
+}
+
+func (type2 *UnsafeSliceType) UnsafeCap(ptr unsafe.Pointer) int {
+	return (*sliceHeader)(ptr).Cap
+}
+
+func (type2 *UnsafeSliceType) Grow(obj interface{}, newLength int) {
+	objEFace := unpackEFace(obj)
+	assertType("SliceType.Grow argument 1", type2.ptrRType, objEFace.rtype)
+	type2.UnsafeGrow(objEFace.data, newLength)
+}
+
+func (type2 *UnsafeSliceType) UnsafeGrow(obj unsafe.Pointer, newLength int) {
+	header := (*sliceHeader)(obj)
+	if newLength <= header.Cap {
+		header.Len = newLength
+		return
+	}
+	newCap := calcNewCap(header.Cap, newLength)
+	newHeader := (*sliceHeader)(type2.UnsafeMakeSlice(header.Len, newCap))
+	typedslicecopy(type2.elemRType, *newHeader, *header)
+	header.Data = newHeader.Data
+	header.Cap = newHeader.Cap
+	header.Len = newLength
+}
+
+func calcNewCap(cap int, expectedCap int) int {
+	if cap == 0 {
+		cap = expectedCap
+	} else {
+		for cap < expectedCap {
+			if cap < 1024 {
+				cap += cap
+			} else {
+				cap += cap / 4
+			}
+		}
+	}
+	return cap
+}