Update README.md

Author: dcarbone

README.md

@@ -63,7 +63,11 @@ Fails validation if the attribute's value matches the user-defined regular expre
 will attempt to convert the attribute to a string first.
 
 ```go
-v := validation.RegexpNotMatch("{{ your regex here }}")
+{
+    Validators: []tfsdk.AttributeValidator{
+    	validation.RegexpNotMatch("{{ your regex here }}")
+    },
+}
 ```
 
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