refactor to use app package instead of service

refactor app to be composable

internal/app/lifecycle.go

@@ -0,0 +1,21 @@
+package app
+
+type Lifecycle struct {
+	cleanups []func()
+}
+
+func NewLifecycle() *Lifecycle {
+	return &Lifecycle{
+		cleanups: make([]func(), 0),
+	}
+}
+
+func (l *Lifecycle) Add(fn func()) {
+	l.cleanups = append(l.cleanups, fn)
+}
+
+func (l *Lifecycle) Close() {
+	for i := len(l.cleanups) - 1; i >= 0; i-- {
+		l.cleanups[i]()
+	}
+}