Locking mechanics with named locks for async operations. After finishing lock code block this code releases semaphore itself. Standard "lock" statement can't be used with async operations: https://stackoverflow.com/a/7612714/47672

SemaphoreLocker.cs

    // Usage example:
    // static readonly SemaphoreLocker _semaphoreLocker = new SemaphoreLocker();
    // var values = await _semaphoreLocker.LockAsync(valuesKey, async () => { return await SomeActionAsync(); });
    
    
    public class SemaphoreLocker
    {
        static readonly ConcurrentDictionary<string, SemaphoreSlim> lockDictionary = new ConcurrentDictionary<string, SemaphoreSlim>();

        public async Task LockAsync(string key, Func<Task> worker)
        {
            SemaphoreSlim semaphore = lockDictionary.GetOrAdd(key, new SemaphoreSlim(1, 1));
            await semaphore.WaitAsync();
            try
            {
                await worker();
            }
            finally
            {
                semaphore.Release();
                lockDictionary.TryRemove(key, out semaphore);
            }
        }

        // Overloading variant for non-void methods with return type (generic T)
        public async Task<T> LockAsync<T>(string key, Func<Task<T>> worker)
        {
            SemaphoreSlim semaphore = lockDictionary.GetOrAdd(key, new SemaphoreSlim(1, 1));
            await semaphore.WaitAsync();
            try
            {
                return await worker();
            }
            finally
            {
                semaphore.Release();
                lockDictionary.TryRemove(key, out semaphore);
            }
        }
    }