The current doc does not really make that clear. In most scala programs imports are located at the top.
It is mandatory to me to highlight that a Future and all asynchronous operations performed on a future require an ExecutionContext. That's why I suggest to first show a Future with an ExecutionContext explicitly passed, then having it implicitly passed in the scope where you need it (having an `implicit val` removes ambiguities) and finally use the `import ExecutionContext.Implicit.global`.