exercise 11 added

src/functional/11_run_once.py

@@ -0,0 +1,21 @@
+import functools
+
+def run_once(f):
+    already_run = False
+
+    @functools.wraps(f)
+    def wrapper(*args, **kwargs):
+        nonlocal already_run
+
+        if not already_run:
+            already_run = True
+            return f(*args, **kwargs)
+
+    return wrapper
+
+@run_once
+def test():
+    print("Hello World!")
+
+test()
+test()