Try to fix envsuvst output of $

entrypoint.sh

 #! /bin/sh
+export dollar='$'
 cat /etc/nginx/site.conf|envsubst>/etc/nginx/sites-enabled/default
 exec "$@"

nginx/site.conf

@@ -4,7 +4,7 @@ server {
 
         location / {
                 proxy_pass http://localhost:${upstream_port};
-                set $$feide_mode '${feide_mode}';
+                set ${dollar}feide_mode '${feide_mode}';
                 rewrite_by_lua_file /usr/local/share/lua/5.1/feide.lua;
         }