support handling CLOSED messages from relay client.

subscription.go

@@ -26,11 +26,15 @@ type Subscription struct {
 	// the EndOfStoredEvents channel gets closed when an EOSE comes for that subscription
 	EndOfStoredEvents chan struct{}
 
+	// the ClosedReason channel emits the reason when a CLOSED message is received
+	ClosedReason chan string
+
 	// Context will be .Done() when the subscription ends
 	Context context.Context
 
 	live   atomic.Bool
 	eosed  atomic.Bool
+	closed atomic.Bool
 	cancel context.CancelFunc
 
 	// this keeps track of the events we've received before the EOSE that we must dispatch before
@@ -107,6 +111,13 @@ func (sub *Subscription) dispatchEose() {
 	}
 }
 
+func (sub *Subscription) dispatchClosed(reason string) {
+	if sub.closed.CompareAndSwap(false, true) {
+		sub.ClosedReason <- reason
+		close(sub.ClosedReason)
+	}
+}
+
 // Unsub closes the subscription, sending "CLOSE" to relay as in NIP-01.
 // Unsub() also closes the channel sub.Events and makes a new one.
 func (sub *Subscription) Unsub() {