Tour of Go 2.0

Maps

Maps associate keys with values — like a dictionary or hash table.

The zero value of a map is nil. A nil map has no keys and you can’t add any. To get a usable map, initialize it with make:

m = make(map[string]Vertex)

That gives you an empty map, ready to use.

Try it: Add a second location to the map and print it.

main.go ▶ Run in Playground 
package main

import "fmt"

type Vertex struct {
	Lat, Long float64
}

var m map[string]Vertex

func main() {
	m = make(map[string]Vertex)
	m["Bell Labs"] = Vertex{
		40.68433, -74.39967,
	}
	fmt.Println(m["Bell Labs"])
}