There was an error with the transport. [javascript]

[win9s]

when signalr is reconnecting, i need to find out the specific reson when reconnect failed, but i got the same error "There was an error with the transport." , even the real error is token expired, and i viewd source code, here are the specific locations:

// WebSocketTransport.ts 
webSocket.onerror = (event: Event) => {
    let error: any = null;
    // ErrorEvent is a browser only type we need to check if the type exists before using it
    if (typeof ErrorEvent !== "undefined" && event instanceof ErrorEvent) {
        error = event.error;
    } else {
        error = new Error("There was an error with the transport.");
    }

    reject(error);
};

my program runs in a node environment, the original error has been converted

how can I get the original error? Or is this considered a bug?

by the way, I redefined the logic of reconnection, although I don't think this is related to the problem.

any response would be appreciated!