tracker: Add common interface to start and stop servers

tracker/tracker.go

@@ -24,6 +24,15 @@ type Tracker struct {
 	*Storage
 }
 
+// Server represents a server for a given BitTorrent tracker protocol.
+type Server interface {
+	// Serve runs the server and blocks until the server has shut down.
+	Serve()
+
+	// Stop cleanly shuts down the server in a non-blocking manner.
+	Stop()
+}
+
 // New creates a new Tracker, and opens any necessary connections.
 // Maintenance routines are automatically spawned in the background.
 func New(cfg *config.Config) (*Tracker, error) {