[client] IPv6 friendly connection

parsedURL.Hostname() strips IPv6 brackets. For http://[::1]:443, this turns it into ::1:443, which is not a valid host:port target for gRPC. Additionally, fmt.Sprintf("%s:%s", hostname, port) produces a trailing colon when the URL has no explicit port—http://example.com becomes example.com:. Both cases break the initial dial and reconnect paths. Use parsedURL.Host directly instead.

flow/client/client.go

@@ -75,7 +75,7 @@ func NewClient(addr, payload, signature string, interval time.Duration) (*GRPCCl
 		grpc.WithDefaultServiceConfig(`{"healthCheckConfig": {"serviceName": ""}}`),
 	)
 
-	target := fmt.Sprintf("%s:%s", parsedURL.Hostname(), parsedURL.Port())
+	target := parsedURL.Host
 	conn, err := grpc.NewClient(target, opts...)
 	if err != nil {
 		return nil, fmt.Errorf("creating new grpc client: %w", err)