Updater loop with period and http route (#240)

* Updater loop with period and http route
* Using DNS over TLS to update servers
* Better logging
* Remove goroutines for cyberghost updater
* Respects context for servers update (quite slow overall)
* Increase shutdown grace period to 5 seconds
* Update announcement
* Add log lines for each provider update start

internal/updater/surfshark.go

@@ -30,6 +30,9 @@ func findSurfsharkServers(ctx context.Context, lookupIP lookupIPFunc) (servers [
 		return nil, err
 	}
 	for fileName, content := range contents {
+		if err := ctx.Err(); err != nil {
+			return nil, err
+		}
 		if strings.HasSuffix(fileName, "_tcp.ovpn") {
 			continue // only parse UDP files
 		}