Add peer discovery (cosmos#17)

* Use DHT for bootstrapping and active peer discovery
* Pass context instead of storing it in struct
* Wrap libp2p host with RoutedHost
* Ensure that context passed to libp2p is cancelled

Resolves cosmos#2.

config/defaults.go

@@ -0,0 +1,5 @@
+package config
+
+const (
+	DefaultListenAddress = "/ip4/0.0.0.0/tcp/7676"
+)

go.mod

@@ -3,10 +3,12 @@ module github.com/lazyledger/optimint
 go 1.15
 
 require (
+	github.com/ipfs/go-log v1.0.4
 	github.com/lazyledger/lazyledger-core v0.0.0-20210219190522-0eccfb24e2aa
-	github.com/libp2p/go-libp2p v0.13.0 // indirect
+	github.com/libp2p/go-libp2p v0.13.0
 	github.com/libp2p/go-libp2p-core v0.8.5
-	github.com/multiformats/go-multiaddr v0.3.1 // indirect
-	github.com/multiformats/go-multihash v0.0.14 // indirect
+	github.com/libp2p/go-libp2p-discovery v0.5.0
+	github.com/libp2p/go-libp2p-kad-dht v0.11.1
+	github.com/multiformats/go-multiaddr v0.3.1
 	github.com/stretchr/testify v1.7.0
 )