/// <summary>
/// Tries to add a value associated to the <paramref name="key"/> if it doesn't exist.
/// </summary>
public static Task <TValue> AddOrGet <TKey, TValue>(
this IStorage <TKey, TValue> storage,
TKey key,
TValue value,
CancellationToken token = default) =>
storage.AddOrGet(key, _ => Task.FromResult(value), token);
/// <summary>
/// Tries to add a value associated to the <paramref name="key"/> if it doesn't exist.
/// </summary>
public static Task <TValue> AddOrGet <TKey, TValue>(
this IStorage <TKey, TValue> storage,
TKey key,
Func <TKey, TValue> addFactory) =>
storage.AddOrGet(key, x => Task.FromResult(addFactory(x)));