Event bus in Go (research)

- What are the best solutions for implementing an internal event bus in Go so that different services can subscribe, consume and publish events asynchronously? 
- How would the interfaces look like?

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Related to https://github.com/libp2p/go-libp2p/issues/467 and https://github.com/libp2p/go-libp2p-kad-dht/issues/331