Use the environment variable directly

config/root/etc/nginx/token_server.conf

@@ -11,18 +11,19 @@ server {
     # Server domain name
     server_name _;
 
-    set_by_lua_block $pot_url_scheme {
-        local haystack = os.getenv('YT_POT_BGUTIL_BASE_URL') or ''
-        local needle = 'https://'
-        local scheme = 'http'
-        if haystack:sub(1, #needle) == needle then
-            scheme = 'https'
+    set_by_lua_block $pot_url {
+        local default = 'http://token_server'
+        local url = os.getenv('YT_POT_BGUTIL_BASE_URL')
+        if not url then
+            return default
         end
-        return scheme
+        if #url and url:find('://') then
+            return url
+        end
+        return default
     }
 
     location / {
-        proxy_pass $pot_url_scheme://token_server;
-        proxy_redirect default;
+        proxy_pass $pot_url;
     }
 }