What types of data can serve as a key in a map container?

In Go, the key in a map can only be of types that are comparable. This means that the key type must have the == operator defined.

Suitable key types:

• Boolean values (bool)
• Numbers (int, float64, uint8, etc.)
• Strings (string)
• Pointers
• Channels
• Interfaces, if the dynamic type is comparable
• Structs, if all their fields are comparable

Cannot be used as keys:

• Slices (slice)
• Maps (map)
• Functions

Example:

m := make(map[string]int)
m["key"] = 42

// Struct with comparable fields
type Point struct {
    X, Y int
}

m2 := make(map[Point]string)
m2[Point{1,2}] = "A point"

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