What types of keys are possible to use in a Map data structure?

In Go, keys for the map data structure can be any types that support comparison with == and !=. This means keys can be:

• Boolean values (bool)
• Numeric types (int, float64, etc.)
• Strings (string)
• Pointers
• Structs, if all their fields are comparable

Slices (slice), maps (map), and functions cannot be used as keys because they are not comparable.

Example of using a map with a string key:

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

If you need to use complex keys, you can define a struct with comparable fields.