Add test to verify sync.Mutex internal layout

trylock_test.go

@@ -1,6 +1,22 @@
 package trylock
 
-import "testing"
+import (
+	"reflect"
+	"testing"
+)
+
+func TestMutexLayout(t *testing.T) {
+	sf := reflect.TypeOf((*Mutex)(nil)).Elem().FieldByIndex([]int{0, 0})
+	if sf.Name != "state" {
+		t.Fatal("sync.Mutex first field should have name state")
+	}
+	if sf.Offset != uintptr(0) {
+		t.Fatal("sync.Mutex state field should have zero offset")
+	}
+	if sf.Type != reflect.TypeOf(int32(1)) {
+		t.Fatal("sync.Mutex state field type should be int32")
+	}
+}
 
 func TestTryLock(t *testing.T) {
 	var mu Mutex