I'm afraid I don't understand the purpose of this. Are there servers that die if you don't hit their URLs periodically? I use uptimerobot for my servers but it serves a different purpose.
For FaaS (like Lambda), if a function hasn't been hit in a while, it'll be cold started when it is needed next. (Even though it's "serverless" behind the scenes they're likely containers that stay up for a little while to handle subsequent requests; a cold start means there's overhead of starting up the container)
A hack to keep your function warm is to call it via cron or a service like this.
A hack to keep your function warm is to call it via cron or a service like this.