map literal in Go
Map literals are like struct literals, but the keys are required. If the top-level type is just a type name, you can omit it from the elements of the literal. ``` var m = map[string]int{ "x": 1, "y": 2, } var m = map[string]Vertex{ "Bell Labs": {40.68433, -74.39967}, "Google": {37.42202, -122.08408}, } ```