An *OrderedMap is a high performance ordered map that maintains amortized O(1) for Set, Get, Delete and Len:

import "github.com/elliotchance/orderedmap/v2" func main() { m := orderedmap.NewOrderedMap[string, any]() m.Set("foo", "bar") m.Set("qux", 1.23) m.Set("123", true) m.Delete("qux") }

Note: v2 requires Go v1.18 for generics. If you need to support Go 1.17 or below, you can use v1.

Internally an *OrderedMap uses the composite type map combined with a trimmed down linked list to maintain the order.

Be careful using Keys() as it will create a copy of all of the keys so it's only suitable for a small number of items:

for _, key := range m.Keys() { value, _:= m.Get(key) fmt.Println(key, value) }

For larger maps you should use Front() or Back() to iterate per element:

// Iterate through all elements from oldest to newest: for el := m.Front(); el != nil; el = el.Next() { fmt.Println(el.Key, el.Value) } // You can also use Back and Prev to iterate in reverse: for el := m.Back(); el != nil; el = el.Prev() { fmt.Println(el.Key, el.Value) }

The iterator is safe to use bidirectionally, and will return nil once it goes beyond the first or last item.

If the map is changing while the iteration is in-flight it may produce unexpected behavior.