var m map[string]int
m = make(map[string]int)
m["key"] = 42
fmt.Println(m["key"])

// delete key from a map
delete(m, "key")

// test if key "key" is present and retrieve it, if so
elem, ok := m["key"]

// map literal
var m = map[string]Vertex{
    "Bell Labs": {40.68433, -74.39967},
    "Google":    {37.42202, -122.08408},
}