Go: Design Patterns for Real-World Projects

The map type

The Go map is a composite type that is used as containers for storing unordered elements of the same type indexed by an arbitrary key value. The following code snippet shows a variety of map variables declarations with a variety of key types:

var ( 
    legends map[int]string 
    histogram map[string]int 
    calibration map[float64]bool 
    matrix map[[2][2]int]bool    // map with array key type 
    table map[string][]string    // map of string slices 
 
   // map (with struct key) of map of string 
   log map[struct{name string}]map[string]string 
) 

golang.fyi/ch07/maptypes.go

The previous code snippet shows several variables declared as maps of different types with a variety of key types. In general, map type is specified as follows:

map[<key_type>]<element_type>

The