What data types can be used as keys in a map?

In Go, map keys can only be types that support comparison operations for equality (== and !=). This is because maps use hashing and key comparison to find values.

Suitable key types:

• Boolean values (bool)
• Numbers (int, float64, uint, etc.)
• Strings (string)
• Pointers
• Channels
• Interfaces, if the dynamic type of the key supports comparison
• Structs, if all their fields are comparable

Cannot be used:

• Slices
• Maps
• Functions

Example of using a map with a struct type as a key:

package main
import "fmt"

type Point struct {
    X, Y int
}

func main() {
    m := make(map[Point]string)
    m[Point{1, 2}] = "A"
    fmt.Println(m[Point{1, 2}]) // Will print "A"
}

Attempting to use a non-comparable type as a key will result in a compile-time error.