Maps
8 min · Go
Look up values by key with map — Go's dictionary.
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Key-value lookups with map
Where a slice looks values up by numeric position, a map looks values up by a meaningful key instead — a player's name, an item id. map[string]int describes the type: a map whose keys are strings and whose values are ints. make(map[string]int) creates an empty one, ready to have entries added.
m[key] = value stores an entry, and m[key] reads one back — the same square-bracket syntax you already know from slices, just keyed by something other than a plain integer index. If you read a key that was never stored, Go quietly gives you the zero value for that value type (0 for int, "" for string) instead of crashing, which is worth knowing since a typo'd key won't necessarily produce an obvious error.
Every mainstream language has its own version of this idea — a dict in Python, an object or Map in JavaScript, a Dictionary in C# — because looking things up by a meaningful name rather than position is such a universally common need.
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