What are the properties and requirements for keys in a map data structure?

In Go, keys in a map data structure must meet the following requirements:

• Keys must be comparable. This means the key type must support the comparison operations == and !=. For example, basic types (int, string, bool), pointers, and interfaces with comparable values are suitable.
• Slices, maps, and functions cannot be used as keys because they are not comparable.

Example of creating a map with string keys:

m := make(map[string]int)
 m["one"] = 1
 m["two"] = 2

Trying to use an incomparable type, such as a slice, will result in a compile-time error:

var s []int
m := make(map[[]int]string) // error: invalid map key type []int

Therefore, keys must be of types that can be compared for the map to work correctly.