Go編程提供另一個重要的數據類型是映射，唯一映射一個鍵到一個值。一個鍵要使用在以後檢索值的對象。給定的鍵和值，可以在一個Map對象存儲的值。值存儲後，您可以使用它的鍵檢索。

定義映射

必須使用make函數來創建一個映射。

/* declare a variable, by default map will be nil*/
var map_variable map[key_data_type]value_data_type

/* define the map as nil map can not be assigned any value*/
map_variable = make(map[key_data_type]value_data_type)

例子

下麵的例子說明創建和映射的使用。

package main

import "fmt"

func main {
   var coutryCapitalMap map[string]string
   /* create a map*/
   coutryCapitalMap = make(map[string]string)
   
   /* insert key-value pairs in the map*/
   countryCapitalMap["France"] = "Paris"
   countryCapitalMap["Italy"] = "Rome"
   countryCapitalMap["Japan"] = "Tokyo"
   countryCapitalMap["India"] = "New Delhi"
   
   /* print map using keys*/
   for country := range countryCapitalMap {
      fmt.Println("Capital of",country,"is",countryCapitalMap[country])
   }
   
   /* test if entry is present in the map or not*/
   captial, ok := countryCapitalMap["United States"]
   /* if ok is true, entry is present otherwise entry is absent*/
   if(ok){
      fmt.Println("Capital of United States is", capital)  
   }else {
      fmt.Println("Capital of United States is not present") 
   }
}

讓我們編譯和運行上麵的程序，這將產生以下結果：

Capital of India is New Delhi
Capital of France is Paris
Capital of Italy is Rome
Capital of Japan is Tokyo
Capital of United States is not present

delete() 函數

delete()函數是用於從映射中刪除一個項目。映射和相應的鍵將被刪除。下麵是一個例子：

package main

import "fmt"

func main {   
   /* create a map*/
   coutryCapitalMap := map[string] string {"France":"Paris","Italy":"Rome","Japan":"Tokyo","India":"New Delhi"}
   
   fmt.Println("Original map")   
   
   /* print map */
   for country := range countryCapitalMap {
      fmt.Println("Capital of",country,"is",countryCapitalMap[country])
   }
   
   /* delete an entry */
   delete(countryCapitalMap,"France");
   fmt.Println("Entry for France is deleted")  
   
   fmt.Println("Updated map")   
   
   /* print map */
   for country := range countryCapitalMap {
      fmt.Println("Capital of",country,"is",countryCapitalMap[country])
   }
}

讓我們編譯和運行上麵的程序，這將產生以下結果：

Original Map
Capital of France is Paris
Capital of Italy is Rome
Capital of Japan is Tokyo
Capital of India is New Delhi
Entry for France is deleted
Updated Map
Capital of India is New Delhi
Capital of Italy is Rome
Capital of Japan is Tokyo