use fx lifecycle hooks to start and stop services

[marten-seemann]

Starting and stopping services on the host has long been a pain point. By using fx's lifecycle hooks we could potentially dramatically simplify our code base.

This is the Close logic in the BasicHost:

go-libp2p/p2p/host/basic/basic_host.go

Lines 972 to 1011 in c48e78f

	func (h *BasicHost) Close() error {
	h.closeSync.Do(func() {
	h.ctxCancel()
	if h.natmgr != nil {
	h.natmgr.Close()
	}
	if h.cmgr != nil {
	h.cmgr.Close()
	}
	if h.ids != nil {
	h.ids.Close()
	}
	if h.autoNat != nil {
	h.autoNat.Close()
	}
	if h.relayManager != nil {
	h.relayManager.Close()
	}
	if h.hps != nil {
	h.hps.Close()
	}
	_ = h.emitters.evtLocalProtocolsUpdated.Close()
	_ = h.emitters.evtLocalAddrsUpdated.Close()
	h.Network().Close()
	h.psManager.Close()
	if h.Peerstore() != nil {
	h.Peerstore().Close()
	}
	h.refCount.Wait()
	if h.Network().ResourceManager() != nil {
	h.Network().ResourceManager().Close()
	}
	})
	return nil
	}

There also exist wrapped hosts only for hooking into the Close method, for example here:

go-libp2p/p2p/host/autorelay/host.go

Lines 7 to 15 in c48e78f

	type AutoRelayHost struct {
	host.Host
	ar *AutoRelay
	}
	func (h *AutoRelayHost) Close() error {
	_ = h.ar.Close()
	return h.Host.Close()
	}