upstream gitlab-workhorse {
    server unix:/var/opt/gitlab/gitlab-workhorse/socket;
}

server {
    listen 0.0.0.0:80 default_server;
    server_name git.mydomain.ru
    server_tokens off;
    root /opt/gitlab/embedded/service/gitlab-rails/public;

    access_log  /var/log/nginx/gitlab.access.log;
    error_log   /var/log/nginx/gitlab.error.log;

    location / {
        client_max_body_size 0;
        gzip off;
        proxy_read_timeout      300;
        proxy_connect_timeout   300;
        proxy_redirect          off;
        proxy_http_version 1.1;
        proxy_set_header    Host                $http_host;
        proxy_set_header    X-Real-IP           $remote_addr;
        proxy_set_header    X-Forwarded-For     $proxy_add_x_forwarded_for;
        proxy_set_header    X-Forwarded-Proto   $scheme;
        proxy_pass http://gitlab-workhorse;
    }
}

$ sudo nginx -c /etc/nginx/sites-enabled/gitlab.conf -t
 nginx: [emerg] "upstream" directive is not allowed here in /etc/nginx/sites-enabled/gitlab.conf:1
 nginx: configuration file /etc/nginx/sites-enabled/gitlab.conf test failed