feat: release managed service generation and contract diagnostics

examples/managedService/internal/svc/close.go

@@ -0,0 +1,36 @@
+package svc
+
+import "errors"
+
+// Close is idempotent, including startup failure and graceful shutdown.
+func (c *ServiceContext) Close() error {
+	if c == nil {
+		return nil
+	}
+	c.closeOnce.Do(func() {
+		c.closeMu.Lock()
+		c.closed = true
+		cleanups := c.cleanups
+		c.cleanups = nil
+		c.closeMu.Unlock()
+		for i := len(cleanups) - 1; i >= 0; i-- {
+			c.closeErr = errors.Join(c.closeErr, cleanups[i]())
+		}
+
+	})
+	return c.closeErr
+}
+
+// OnClose transfers a resource cleanup to this context immediately after creation.
+// Hooks run once in reverse order, also when later initialization fails.
+func (c *ServiceContext) OnClose(cleanup func() error) {
+	if cleanup == nil {
+		return
+	}
+	c.closeMu.Lock()
+	defer c.closeMu.Unlock()
+	if c.closed {
+		panic("svc: register cleanup after Close")
+	}
+	c.cleanups = append(c.cleanups, cleanup)
+}