What is a map in Go, how does it work, and what are its features?

In Go, a map is a built-in data type that implements an associative array or dictionary, where keys are mapped to values.

Features of map in Go:

• Keys can be of any type that supports comparison (e.g., strings, numbers, pointers).
• Values can be of any type.
• Can be initialized using make or a literal:

m := make(map[string]int)

m2 := map[string]int{"a": 1, "b": 2}

• Access to elements via m[key], if the key is absent — the zero value of the type is returned.
• Checking for the presence of a key:

val, ok := m["key"]
if ok {
    // key exists
}

• map does not guarantee the order of traversal of elements.
• map is not thread-safe; synchronization is needed for concurrent access.

Example:

m := make(map[string]int)
m["apple"] = 5
fmt.Println(m["apple"]) // 5

val, ok := m["banana"]
if !ok {
    fmt.Println("banana not found")
}