extract subscription to separate file

waku/v2/node/subscription.go

@@ -0,0 +1,26 @@
+package node
+
+import (
+	"sync"
+
+	"github.com/status-im/go-waku/waku/common"
+)
+
+type Subscription struct {
+	C      chan *common.Envelope
+	closed bool
+	mutex  sync.Mutex
+	quit   chan struct{}
+}
+
+func (subs *Subscription) Unsubscribe() {
+	if !subs.closed {
+		close(subs.quit)
+	}
+}
+
+func (subs *Subscription) IsClosed() bool {
+	subs.mutex.Lock()
+	defer subs.mutex.Unlock()
+	return subs.closed
+}