Pattern for getting an Access Token ONLY when its about to expire

I’m working on an ASP Net Core project where I have to get an Access Token in order to call an external endpoint. This Access Token has a 5 min lifespan. Is there a pattern for only calling the GetAccessToken function ONLY when its about to expire and NOT called it on each request coming in?

Note: I Can have up to 200 request in 5 minutes hence the question