What is the maximum possible time to retrieve a value by key in a map data structure?

In Go, access to a map element by key is performed in amortized O(1) time, which is constant on average. However, in the worst case, such as when there are many hash collisions, the time can degrade to O(n), where n is the number of elements in the map. In practice, thanks to a good hash table implementation and key randomization, access is very fast and close to constant time.