[@sentry/tracing][express] Span is lost for last middleware

[xr0master]

issue

It happens because of event finish order.
In handler:
https://github.com/getsentry/sentry-javascript/blob/master/packages/node/src/handlers.ts#L65
In express
https://github.com/getsentry/sentry-javascript/blob/master/packages/tracing/src/integrations/express.ts#L121

The handlers listener fires before express, as result the last spin has been filtered in:
https://github.com/getsentry/sentry-javascript/blob/master/packages/tracing/src/transaction.ts#L90
because the last span still doesn't have the endTimestamp

2 options to fix this issue:

1. use close listener instead of finish in handlers.ts. The close event runs after finish.

res.once('close', () => {
    transaction.setHttpStatus(res.statusCode);
    transaction.finish();
});

2. finish all spans if transaction.finish(); runs

const finishedSpans = this.spanRecorder ? this.spanRecorder.spans
    .reduce((spans, s) => {
        !s.endTimestamp && s.finish();
        s !== this && spans.push(s);

        return spans;
    }, []) : [];

Let me know which option is best for you.

[xr0master]

any updates?