LittleBookOfSemaphores | Go Language take on Allen Downey | Learning library

I am currently trying to solve the 'unisex bathroom' problem found in [this book],(http://greenteapress.com/semaphores/LittleBookOfSemaphores.pdf) the constraints are: - if the bathroom is empty, either male or female can enter - if a male or female is in the bathroom, only the same gender can enter - there can only be two people in the bathroom already

What is confusing me is although I have some understanding of the concepts of how the logic works, I am not sure where/how to implement this code. Eg, I have a class named 'employee' which extends thread and can set a variable that shows if they are male or female. I also have a 'bathroom' class that also extends thread that contains the semaphore called 'being used' which is to determine if the bathroom is full. I was trying to implement the lightswitch structure found in the book, which i assume is just a monitor. I do not understand how this locks for a specific type of thread.

My question is, where do I store the semaphore variables, and what is the best way to access them in order to implement the rest of the logic?

EDIT: When I refer to the lightswitch I mean the struct on page 70, and the bathroom problem is located on page 170.

Bathroom class contains: