Proxy Grafana Live WebSocket connections

[sinedoOo]

In official guide of Grafana there is example configuration for Nginx.

# this is required to proxy Grafana Live WebSocket connections.
map $http_upgrade $connection_upgrade {
  default upgrade;
  '' close;
}

upstream grafana {
  server localhost:3000;
}

server {
  listen 80;
  root /usr/share/nginx/html;
  index index.html index.htm;

  location / {
    proxy_set_header Host $http_host;
    proxy_pass http://grafana;
  }

# Proxy Grafana Live WebSocket connections.
  location /api/live/ {
    proxy_http_version 1.1;
    proxy_set_header Upgrade $http_upgrade;
    proxy_set_header Connection $connection_upgrade;
    proxy_set_header Host $http_host;
    proxy_pass http://grafana;
  }
}

Unfortunately I cannot force the live WebSockets to work. Any help how I can configure it in Unit? Simple config with proxy works except broken WebSockets requests.