ok find the solution for those who use apache2.4 on debian jessie 8
use this vhost
<VirtualHost *:80>
ServerName git.example.com
DocumentRoot /opt/gitlab/embedded/service/gitlab-rails/public
ProxyPreserveHost On
AllowEncodedSlashes NoDecode
RewriteEngine on
RewriteCond %{DOCUMENT_ROOT}/%{REQUEST_FILENAME} !-f
RewriteRule .* http://127.0.0.1:8080%{REQUEST_URI} [P,QSA]
and put this in gitlab.rb
gitlab_workhorse[‘listen_network’] = “tcp”
gitlab_workhorse[‘listen_addr’] = “127.0.0.1:8181”