in src/directLine.ts [617:624]
private expiredToken() {
const connectionStatus = this.connectionStatus$.getValue();
if (connectionStatus != ConnectionStatus.Ended && connectionStatus != ConnectionStatus.FailedToConnect)
this.connectionStatus$.next(ConnectionStatus.ExpiredToken);
const protectedConnectionStatus = this.expiredTokenExhaustion(this.connectionStatus$.getValue());
this.connectionStatus$.next(protectedConnectionStatus);
}