Where is the IDistributedCache implementation for memory cache?

Reading the article of caching in ASP.Net Core I can see that an implementation of the IDistributedCache as in-memory cache exists:

https://docs.microsoft.com/es-es/aspnet/core/performance/caching/distributed?view=aspnetcore-5.0#distributed-memory-cache

Where can I find this implementation?

Context:

I want to implement the IDistributedCache but use it as in-memory cache at the moment. Later we will switch to Redis using the same interface.