SrtSocket.Close() leaks callbacks due to overwriting socket before map cleanup

[ditogam]

SrtSocket.Close() leaks callbacks due to overwriting socket before cleanup

Description
(*SrtSocket).Close() sets s.socket = SRT_INVALID_SOCK before attempting to clean up listenCallbackMap and connectCallbackMap.
Because the socket value is overwritten too early, the map lookups always fail. This results in:

• gopointer.Unref never being called → memory leaks
• map entries never being removed → map leaks

---

Current Code (buggy)

func (s *SrtSocket) Close() {
    C.srt_close(s.socket)
    s.socket = SRT_INVALID_SOCK
    if !s.blocking {
        s.pd.close()
    }
    callbackMutex.Lock()
    if ptr, exists := listenCallbackMap[s.socket]; exists {
        gopointer.Unref(ptr)
    }
    if ptr, exists := connectCallbackMap[s.socket]; exists {
        gopointer.Unref(ptr)
    }
    callbackMutex.Unlock()
}

Proposed Fix

func (s *SrtSocket) Close() {
    sock := s.socket
    if sock == SRT_INVALID_SOCK {
        return
    }

    callbackMutex.Lock()
    if ptr, ok := listenCallbackMap[sock]; ok {
        gopointer.Unref(ptr)
        delete(listenCallbackMap, sock)
    }
    if ptr, ok := connectCallbackMap[sock]; ok {
        gopointer.Unref(ptr)
        delete(connectCallbackMap, sock)
    }
    callbackMutex.Unlock()

    if !s.blocking && s.pd != nil {
        s.pd.close()
    }

    C.srt_close(sock)
    s.socket = SRT_INVALID_SOCK
}