Hands-On System Programming with Go

Maps

A map type allows you to get the type of both value and key, using the Key and Elem methods:

func main() {    maps := []interface{}{        make(map[string]struct{}),        make(map[int]rune),        make(map[float64][]byte),        make(map[int32]chan bool),        make(map[[2]string]interface{}),    }    for _, m := range maps {        t := reflect.TypeOf(m)        fmt.Printf("%s k:%-10s v:%-10s\n", m, t.Key(), t.Elem())    }}

A full example is available here: https://play.golang.org/p/j__1jtgy-56.

The values can be accessed in all the ways that a map can be accessed normally:

• By getting a value using a key
• By ranging over keys
• By ranging over values

Let's see how it works in a practical example:

func main() {    m := map[string]int64{        "a": 10,        "b": 20,        "c": 100,        "d": 42,    } v := reflect.ValueOf(m) ...