Overview

WeakCache provides duplicate function call suppression combined with a weakly referenced cache for storing results.

This means:

Concurrent calls with the same key will be collapsed into a single execution making sure that only one execution is in-flight for a given key at a time.
Results are cached and reused if available — but only as long as they are still held by a weak pointer. Once garbage collected, the result is gone from cache.

WeakCache use modified version of Go’s x/sync/singleflight. The key differences of weakCache singleflight are:

The main difference is that Group is now generic. This means that the function passed to Do has to return a type which was used to create Group.
The DoChan method is removed. I might add it back in the future as a generic version.

Example

w := NewWeakCache[int]()

r, err := w.Do("key", func() (int, error) {
    time.Sleep(10 * time.Microsecond)
    return 1, nil
})

If another goroutine calls Do("key", ...) while the first one is still running, it will block and reuse the results from the first one. This is singleflight behavior.
Later calls to Do("key", ...) will reuse the cached result, as long as it hasn’t been collected by the GC.