Add issue

Author: lucacome

collector/nginx_plus.go

@@ -623,6 +623,7 @@ func (c *NginxPlusCollector) Collect(ch chan<- prometheus.Metric) {
 	c.mutex.Lock() // To protect metrics from concurrent collects
 	defer c.mutex.Unlock()
 
+	// FIXME: https://github.com/nginxinc/nginx-prometheus-exporter/issues/858
 	stats, err := c.nginxClient.GetStats(context.TODO())
 	if err != nil {
 		c.upMetric.Set(nginxDown)