Fix concurrent map access panic in webSocketServer.Close()

Close() iterated s.connections without holding the mutex, while
connection goroutines (listen/sender) concurrently called
connectionClosed() which deletes from the same map under the lock.
This caused a "concurrent map iteration and map write" fatal error
observed as a flaky failure in TestBroadcastStartWithoutConnections.

Snapshot the connections slice under the lock before closing them.

Signed-off-by: Enrique Lacal <enrique.lacal@kaleido.io>
Made-with: Cursor

Author: EnriqueL8

pkg/wsserver/wsserver.go

@@ -127,7 +127,13 @@ func (s *webSocketServer) connectionClosed(c *webSocketConnection) {
 }
 
 func (s *webSocketServer) Close() {
+	s.mux.Lock()
+	conns := make([]*webSocketConnection, 0, len(s.connections))
 	for _, c := range s.connections {
+		conns = append(conns, c)
+	}
+	s.mux.Unlock()
+	for _, c := range conns {
 		c.close()
 	}
 }