Count Instances

Remember that you can check if a key is already present in a map by using the second return value from the index operation.

names := map[string]int{}

if _, ok := names["elon"]; !ok {
    // if the key doesn't exist yet,
    // initialize its value to 0
    names["elon"] = 0
}

Assignment

We have a slice of user ids, and each instance of an id in the slice indicates that a message was sent to that user. We need to count up how many times each user's id appears in the slice to track how many messages they received.

Implement the getCounts function. It should return a map of string -> int so that each int is a count of how many times each string was found in the slice.