Revert vendor directory to support old golang (GOPATH mode)

gomodule is still in progress to migrate for now, hence multus
team decide to keep vendor directory to support build without
gomodule.

vendor/github.com/modern-go/reflect2/unsafe_field.go

@@ -0,0 +1,74 @@
+package reflect2
+
+import (
+	"reflect"
+	"unsafe"
+)
+
+type UnsafeStructField struct {
+	reflect.StructField
+	structType *UnsafeStructType
+	rtype      unsafe.Pointer
+	ptrRType   unsafe.Pointer
+}
+
+func newUnsafeStructField(structType *UnsafeStructType, structField reflect.StructField) *UnsafeStructField {
+	return &UnsafeStructField{
+		StructField: structField,
+		rtype:       unpackEFace(structField.Type).data,
+		ptrRType:    unpackEFace(reflect.PtrTo(structField.Type)).data,
+		structType:  structType,
+	}
+}
+
+func (field *UnsafeStructField) Offset() uintptr {
+	return field.StructField.Offset
+}
+
+func (field *UnsafeStructField) Name() string {
+	return field.StructField.Name
+}
+
+func (field *UnsafeStructField) PkgPath() string {
+	return field.StructField.PkgPath
+}
+
+func (field *UnsafeStructField) Type() Type {
+	return field.structType.cfg.Type2(field.StructField.Type)
+}
+
+func (field *UnsafeStructField) Tag() reflect.StructTag {
+	return field.StructField.Tag
+}
+
+func (field *UnsafeStructField) Index() []int {
+	return field.StructField.Index
+}
+
+func (field *UnsafeStructField) Anonymous() bool {
+	return field.StructField.Anonymous
+}
+
+func (field *UnsafeStructField) Set(obj interface{}, value interface{}) {
+	objEFace := unpackEFace(obj)
+	assertType("StructField.SetIndex argument 1", field.structType.ptrRType, objEFace.rtype)
+	valueEFace := unpackEFace(value)
+	assertType("StructField.SetIndex argument 2", field.ptrRType, valueEFace.rtype)
+	field.UnsafeSet(objEFace.data, valueEFace.data)
+}
+
+func (field *UnsafeStructField) UnsafeSet(obj unsafe.Pointer, value unsafe.Pointer) {
+	fieldPtr := add(obj, field.StructField.Offset, "same as non-reflect &v.field")
+	typedmemmove(field.rtype, fieldPtr, value)
+}
+
+func (field *UnsafeStructField) Get(obj interface{}) interface{} {
+	objEFace := unpackEFace(obj)
+	assertType("StructField.GetIndex argument 1", field.structType.ptrRType, objEFace.rtype)
+	value := field.UnsafeGet(objEFace.data)
+	return packEFace(field.ptrRType, value)
+}
+
+func (field *UnsafeStructField) UnsafeGet(obj unsafe.Pointer) unsafe.Pointer {
+	return add(obj, field.StructField.Offset, "same as non-reflect &v.field")
+}