For the .on, do we need to specify that it's async?

[shamoons]

    this.emitter.on('notification', async msg => await this.onNotification(msg));

Can I just do:

    this.emitter.on('notification', this.onNotification);

I'm not sure what benefit the async offers?

[DenKorn]

+1.
Also, does this library support await for event handlers? As I understand, for now it just causes promise loose.

[reinoute]

Also, why should it be defined inside onModuleInit and not just inside the constructor?