Monomer sometimes hangs on shutdown

[joshklop]

Reproduce:

1. Start devnet
2. Use the example web app to deposit ETH on L2
3. Shutdown Monomer

After examining a core dump, it appears Monomer gets blocked in env.Close when waiting for all websocket subscriptions to finish.

monomer/node/node.go

Line 157 in 7055b06

env.Defer(subscribeWg.Wait)

Based on the CometBFT event bus implementation, it appears that stopping the event bus before waiting on subscriptions would fix the issue. That means swapping the order of this DeferErr call and the Defer linked above:

monomer/node/node.go

Line 107 in 7055b06

env.DeferErr("stop event bus", eventBus.Stop)

Unfortunately, I don't have time to confirm that my understanding of the problem and solution is accurate, but this should be a good start.