Fix a potential panic

Signed-off-by: Lantao Liu <lantaol@google.com>

pkg/store/container/container.go

@@ -39,7 +39,7 @@ type Container struct {
 	// Container IO
 	IO *cio.ContainerIO
 	// StopCh is used to propagate the stop information of the container.
-	store.StopCh
+	*store.StopCh
 }
 
 // Opts sets specific information to newly created Container.
@@ -80,7 +80,7 @@ func WithStatus(status Status, root string) Opts {
 func NewContainer(metadata Metadata, opts ...Opts) (Container, error) {
 	c := Container{
 		Metadata: metadata,
-		StopCh:   store.StopCh(make(chan struct{})),
+		StopCh:   store.NewStopCh(),
 	}
 	for _, o := range opts {
 		if err := o(&c); err != nil {

pkg/store/sandbox/sandbox.go

@@ -37,7 +37,7 @@ type Sandbox struct {
 	// CNI network namespace client
 	NetNS *NetNS
 	// StopCh is used to propagate the stop information of the sandbox.
-	store.StopCh
+	*store.StopCh
 }
 
 // NewSandbox creates an internally used sandbox type. This functions reminds
@@ -46,7 +46,7 @@ func NewSandbox(metadata Metadata, status Status) Sandbox {
 	s := Sandbox{
 		Metadata: metadata,
 		Status:   StoreStatus(status),
-		StopCh:   store.StopCh(make(chan struct{})),
+		StopCh:   store.NewStopCh(),
 	}
 	if status.State == StateNotReady {
 		s.Stop()

pkg/store/util.go

@@ -16,15 +16,35 @@ limitations under the License.
 
 package store
 
+import "sync"
+
 // StopCh is used to propagate the stop information of a container.
-type StopCh chan struct{}
+type StopCh struct {
+	mu     sync.Mutex
+	ch     chan struct{}
+	closed bool
+}
+
+// NewStopCh creates a stop channel. The channel is open by default.
+func NewStopCh() *StopCh {
+	return &StopCh{
+		ch:     make(chan struct{}),
+		closed: false,
+	}
+}
 
 // Stop close stopCh of the container.
-func (ch StopCh) Stop() {
-	close(ch)
+func (s *StopCh) Stop() {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	if s.closed {
+		return
+	}
+	close(s.ch)
+	s.closed = true
 }
 
 // Stopped return the stopCh of the container as a readonly channel.
-func (ch StopCh) Stopped() <-chan struct{} {
-	return ch
+func (s *StopCh) Stopped() <-chan struct{} {
+	return s.ch
 }