# How to represent a user who hasn't churned in training data

I am building a file with sample data that has a bunch of variables:

date, customer_id, amount_spent, number_of_transactions, time_since_last_transaction etc. that i am mapping against days_to_churn

I will train my model using Keras to map the emboldened variables to the italicised days_to_churn. However there are many instances where a user is an active subscriber and this value is blank.

How would I go about incorporating this to ensure that I am not excluding active people from my churn calculations?