Looping a slice or using a mapping is better to retrieve an object

I have a slice which contains around 3000 bson objects. Every object has some nested mappings and one object has an average size of 4 kb. In my code I have to be able to retrieve these objects based on their uid field fast as possible. My original plan was to write a function to simply loop through the original slice and check for the matching uid like object["uid"] == uidToFind. However now I believe it would be better creating one big mapping where the keys are using the uid field and the values using the corresponding object, somehow like this:

m := make(map[string]bson.M)
m["sample_UID_0"] = bsonObjects[0]
m["sample_UID_1"] = bsonObjects[1]
//... continue with the remaining 3000 objects...

My question is, should I favor this solution over looping through the original slice every time? As I don't have millions of objects, I assume it would be a better idea to keep important stuff in one globally available mapping and just simply access them with m["sample_UID"] rather than always loop through the whole slice.

Beyond performance and memory usage there is one main difference between both solution, the way your map is defined can only contain one entry with the same id. Nothing prevents to have multiple times the same id in your array.

In general, if your array is sorted, you can use a dichotomic search which should not raise any visible difference with a search in an map, but you must keep your array sorted when adding new entries. So the benefit of this solution depends if your array is frequently modified. An array should use less memory than a map.

In your specific example, 3000 entries is not that much. Depending on the frequency of the search in data structure, it's not obvious you may notice any difference on the performance side. You may want to use benchmark to check that.