Lucky for you there's an article explaining exactly that: http://blog.golang.org/gos-declaration-syntax

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I like the map. Here's the rules for Conway's Game of Life as a nested map:

    var cgol = map[state]map[int]state{
        alive: {
            0: dead,
            1: dead,
            2: alive,
            3: alive,
            4: dead,
            5: dead,
            6: dead,
            7: dead,
            8: dead,
        },
        dead: {
            0: dead,
            1: dead,
            2: dead,
            3: alive,
            4: dead,
            5: dead,
            6: dead,
            7: dead,
            8: dead,
        },
    }