How to create a map with a custom data type as a key in Go?

To create a map with a custom data type as a key in Go, you need to ensure that the key type is comparable. Go maps require keys to be comparable to determine if two keys are equal or not. Custom types can be used as keys as long as they implement the equality operator (==) and the hash() method.

Here is an example of creating a map with a custom data type as a key in Go:

package main

import (
	"fmt"
)

type Coordinate struct {
	latitude  float64
	longitude float64
}

func main() {
	// Create a map with Coordinate as key and string as value
	myMap := make(map[Coordinate]string)

	// Add data to the map
	myMap[Coordinate{40.7128, -74.0060}] = "New York"
	myMap[Coordinate{34.0522, -118.2437}] = "Los Angeles"

	// Access data from the map
	fmt.Println(myMap[Coordinate{40.7128, -74.0060}]) // Output: New York
	fmt.Println(myMap[Coordinate{34.0522, -118.2437}]) // Output: Los Angeles
}

In this example, we define the Coordinate struct with latitude and longitude fields. We create a map called myMap with Coordinate as the key type and string as the value type. We add elements to the map using Coordinate keys, and then retrieve the corresponding values by providing a Coordinate key.