Fixing typo.

cmd/api/helpers.go

@@ -14,7 +14,7 @@ application struct so it could just be a regular function, rather than a method
 application. But in general, I suggest setting up all your application-specific handlers
 and helpers so that they are methods on application. It helps maintain consistency in
 your code structure, and also future-proofs your code for when those handlers and
-helpers change later and they do need access to dependency.
+helpers change later, and they do need access to dependency.
 
 Retrieve the "id" URL parameter from the current request context, then convert it to
 an integer and return it. If the operation isn't successful, return 0 and an error.