What types of keys are allowed for use in a Map data structure?

In Go, keys for data structures like map must be of comparable types, meaning types that can be used with == and != operators.

Valid key types include:

• Primitive types: int, float64, string, bool, etc.
• Pointers
• Structs, if all their fields are comparable
• Arrays, if their elements are comparable

Invalid key types include:

• Slices ([])
• Maps (map)
• Functions

Example of using a map with string keys:

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

Attempting to use a slice as a key will result in a compile-time error.