in lib/src/server/sse_handler.dart [151:162]
void _handleDisconnect() {
if (_keepAlive == null) {
// Close immediately if we're not keeping alive.
_close();
} else if (!isInKeepAlivePeriod && !_closedCompleter.isCompleted) {
// Otherwise if we didn't already have an active timer and we've not already
// been completely closed, set a timer to close after the timeout period.
// If the connection comes back, this will be cancelled and all messages left
// in the queue tried again.
_keepAliveTimer = Timer(_keepAlive!, _close);
}
}