Clarify usage of load_dot_env() function

doc/going-further/interacting-with-castor/dot-env.md

@@ -18,17 +18,24 @@ Example:
 ```php
 use Castor\Attribute\AsTask;
 use Castor\Context;
+
 use function Castor\load_dot_env;
 
 #[AsTask()]
 function show_database_url(): void
 {
     $env = load_dot_env();
 
-    io()->writeln($env['DATABASE_URL']) ?? throw new \RuntimeException('DATABASE_URL is not defined');
+    io()->writeln($_SERVER['DATABASE_URL'] ?? throw new \RuntimeException('DATABASE_URL is not defined'));
 }
 ```
 
+> [!IMPORTANT]
+> Even if the `load_dot_env()` function returns the env variables as an array,
+> it will only returns variables defined in the .env file. So if one override
+> one variable with true environment variable, it will not be returned. So it's
+> better to use `$_SERVER` in you code to access env variables.
+
 > [!NOTE]
 > You can find more about how `.env` file loading and overloading works on
 > [related Symfony documentation](https://symfony.com/doc/current/configuration.html#configuring-environment-variables-in-env-files).
@@ -40,6 +47,7 @@ You can also create a context that load a `.env` file:
 ```php
 use Castor\Attribute\AsContext;
 use Castor\Context;
+
 use function Castor\load_dot_env;
 
 #[AsContext()]