unable to consume specific amount of messages without waiting with a setTimeout

**Environment Information**
- OS [e.g. Mac, Arch, Windows 10]: RedHat
- Node Version [e.g. 8.2.1]: 10.6.0
- NPM Version [e.g. 5.4.2]: 6.1.0
- C++ Toolchain [e.g. Visual Studio, llvm, g++]:
- node-rdkafka version [e.g. 2.3.3]: 2.3.2

```typescript
// Non-flowing mode
consumer.connect();

consumer
.on('ready', function() {
consumer.subscribe(['librdtesting-01']);

// Read only 1000 messages
consumer.consume(1000); // <---------- This is not working...
})
.on('data', function(data) {
console.log('Message found! Contents below.');
console.log(data.value.toString());
});
```

If i'm replacing the line that I've marked above with the following, then it does work:

```typescript
setTimeout(() => consumer.consume(1000), 60000); // <-- this is working..
```

Could this be related to `node-rdkafka`? or is it something that has to do with my kafka configuration?

Start by reproducing the non-flowing example with node-rdkafka 2.3.2, focusing on the ready, subscribe, consume, and data event sequence shown in the issue. Trace how consume(1000) behaves when called immediately versus after setTimeout. Done means the requested number of messages can be consumed without the delay, with a regression check for the reported sequence.

Written by the indexing model from the issue text.