New aproach for uploading sanic app config.

sanic/app.py

@@ -1460,25 +1460,28 @@ class Sanic:
     # -------------------------------------------------------------------- #
     def update_config(self, config: Union[bytes, str, dict, Any]):
     """Update app.config.  
-
+    
     Note:: only upper case settings are considered.  
-
+    
     You can upload app config by providing path to py file holding settings.  
-
+    
         # /some/py/file  
         A = 1  
         B = 2  
-
-        app.update_config("/some/py/file")  
-
+    
+        app.update_config("${some}/py/file")  
+    
+    Yes you can put environment variable here, but they must be provided in format: ${some_env_var},  
+    and mark that $some_env_var is treated as plain string.  
+    
     You can upload app config by providing dict holding settings.  
-
+    
         d = {"A": 1, "B": 2}  
         app.update_config(d)  
-
+    
     You can upload app config by providing any object holding settings,  
     but in such case config.__dict__ will be used as dict holding settings.  
-
+    
         class C:  
             A = 1  
             B = 2  

sanic/config.py

@@ -81,25 +81,28 @@ class Config(dict):
 
     def update_config(self, config: Union[bytes, str, dict, Any]):
     """Update app.config.  
-
+    
     Note only upper case settings are considered.  
-
+    
     You can upload app config by providing path to py file holding settings.  
-
+    
         # /some/py/file  
         A = 1  
         B = 2  
-
-        config.update_config("/some/py/file")  
-
+    
+        config.update_config("${some}/py/file")  
+    
+    Yes you can put environment variable here, but they must be provided in format: ${some_env_var},  
+    and mark that $some_env_var is treated as plain string.  
+    
     You can upload app config by providing dict holding settings.  
-
+    
         d = {"A": 1, "B": 2}  
         config.update_config(d)  
-
+    
     You can upload app config by providing any object holding settings,  
     but in such case config.__dict__ will be used as dict holding settings.  
-
+    
         class C:  
             A = 1  
             B = 2  
@@ -139,12 +142,14 @@ def strtobool(val):
 
 def load_module_from_file_location(*args, **kwargs):
     """Returns loaded module provided as a file path.  
-
+    
     :param args: look for importlib.util.spec_from_file_location parameters specification  
     :param kwargs: look for importlib.util.spec_from_file_location parameters specification  
-
+    
     So for example You can:  
+    
         some_module = load_module_from_file_location("some_module_name", "/some/path/${some_env_var})  
+    
     Yes you can put environment variable here, but they must be provided in format: ${some_env_var},  
     and mark that $some_env_var is treated as plain string."""