fix Store of Client that can be anything, not empty struct

ws/controller.go

@@ -8,7 +8,7 @@ import (
 type Client struct {
 	Protocol   string      // choosen protocol (Sec-WebSocket-Protocol)
 	Arguments  [][]string  // URI parameters, index 0 is full URI, then matching groups
-	Store      struct{}    // store (for client implementation-specific data)
+	Store      interface{} // store (for client implementation-specific data)
 }
 
 // Represents a websocket controller callback function