Map in Golang

PROGRAM:

package main

import (
    "fmt"
)

func main() {
    /* Declare a map with key type as integer and value type as string */
    var m map[int]string

    /*
     * Map type is a reference type, default value is nil writing to empty
     * gives runtime panic. Initialize map type with the help of make statement
     */
    m = make(map[int]string)

    /* Write data to map */
    m[1] = "John"
    m[2] = "Peter"
    m[3] = "James"
    m[4] = "Steve"
    m[5] = "Bill"

    /* Read from map */
    v, ok := m[3]
    fmt.Println("Avail:", ok, " Name:", v)

    /* Delete from map */
    delete(m, 5)

    v, ok = m[5]
    fmt.Println("Avail:", ok, " Name:", v)

    /* Get Number of items in map */
    count := len(m)
    fmt.Println("Number of items:", count)

    /* Iterate over map using range */
    for key, value := range m {
        fmt.Println(key, "- ", value)
    }
}

OUTPUT:

Avail: true  Name: James
Avail: false  Name: 
Number of items: 4
1 -  John
2 -  Peter
3 -  James
4 -  Steve