initial commit

pkg/locker/locker.go

@@ -0,0 +1,28 @@
+package locker
+
+import "context"
+
+type Locked[T any] struct {
+	state chan *T
+}
+
+func New[T any](initial *T) *Locked[T] {
+	s := &Locked[T]{}
+	s.state = make(chan *T, 1)
+	s.state <- initial
+	return s
+}
+
+func (s *Locked[T]) Modify(ctx context.Context, fn func(*T) error) error {
+	if ctx.Err() != nil {
+		return ctx.Err()
+	}
+
+	select {
+	case state := <-s.state:
+		defer func() { s.state <- state }()
+		return fn(state)
+	case <-ctx.Done():
+		return ctx.Err()
+	}
+}