http_server: metrics: fix data type formatting
@@ -220,7 +220,7 @@ void cb_metrics_prometheus(mk_request_t *request, void *data)
sds = flb_sds_cat(sds, "\"} ", 3);
len = snprintf(tmp, sizeof(tmp) - 1,
- "%lu ", mv.via.u64);
+ "%" PRIu64 " ", mv.via.u64);
sds = flb_sds_cat(sds, tmp, len);
sds = flb_sds_cat(sds, time_str, time_len);
sds = flb_sds_cat(sds, "\n", 1);
