add info on CGI web application debugging

Author: zamronypj

debugging/index.md

@@ -53,10 +53,42 @@ This will compile Fano Framework web application with debugging information.
 
 Back to Visual Studio Code IDE. Open source code file you want to debug and toggle breakpoint at line of interest by clicking on empty area left of line number. Activate *Run* tab click green button on left of *Debug Fano* to start debugging.
 
+This will run application. Open Internet browser and type URL so that breakpoint is hit.
+
 ## Debugging in Lazarus IDE
 
 *TODO*
 
+## Debugging CGI web application
+
+It may be tricky to debug CGI web applications as they are run by web server. However you can simulate running CGI script using `tools/simulate.run.sh` shell script that is generated when you use [Fano CLI](/scaffolding-with-fano-cli) to create project.
+
+To debug CGI web application with Visual Studio Code, edit `launch.json`
+
+```
+{
+    "version": "0.2.0",
+    "configurations": [
+        {
+            "name": "Debug Fano CGI",
+            "type": "gdb",
+            "request": "launch",
+            "target": "./public/app.cgi",
+            "env": {
+                "REQUEST_METHOD": "GET",
+                "REQUEST_URI" : "/some-url",
+                "QUERY_STRING" : "order=123&user_id=12"
+            }
+            "cwd": "${workspaceRoot}",
+            "valuesFormatting": "parseText"
+        }
+    ]
+}
+```
+
+This will simulate run CGI web application when open from Internat browser via URL
+`http://your.app/some-url?order=123&user_id=12`.
+
 ## Explore more
 
 - [Getting started](/getting-started)