Golang : Display list of countries and ISO codes

The code example below will download the JSON formatted data from http://country.io/names.json and unmarshal the data to display a list of all countries in the world.

 package main

 import (
  "encoding/json"
  "fmt"
  "io/ioutil"
  "net/http"
  "os"
 )

 // NOTE : struct doesn't work here due to the nature
 // of the JSON data from country.io
 // it has no field identifiers

 //type Country struct {
 // ISO string
 //}

 func main() {

  resp, err := http.Get("http://country.io/names.json")

  if err != nil {
 fmt.Println(err)
 os.Exit(1)
  }

  defer resp.Body.Close()

  jsonCountriesData, err := ioutil.ReadAll(resp.Body)

  if err != nil {
 fmt.Println(err)
 os.Exit(1)
  }

  //fmt.Println(string(jsonData))

  countriesMap := make(map[string]interface{})

 //NOTE : unmarshal to struct will throw this error message
 // json: cannot unmarshal object into Go value of type


  // Decode JSON into our map
  err = json.Unmarshal([]byte(jsonCountriesData), &countriesMap)

  if err != nil {
 println(err)
 return
  }

  for iso2, name := range countriesMap {
 fmt.Println("ISO2 code:", iso2, "Country name :", name)
  }

 }

and the output :

 ISO2 code: VA Country name : Vatican
 ISO2 code: AW Country name : Aruba
 ISO2 code: TN Country name : Tunisia
 ISO2 code: MC Country name : Monaco
 ISO2 code: SD Country name : Sudan
 ISO2 code: TC Country name : Turks and Caicos Islands
 ISO2 code: AL Country name : Albania
 ISO2 code: PL Country name : Poland
 ISO2 code: LT Country name : Lithuania
 ISO2 code: LU Country name : Luxembourg
 ISO2 code: TH Country name : Thailand
 ISO2 code: PA Country name : Panama
 ISO2 code: PK Country name : Pakistan
 ISO2 code: YE Country name : Yemen
 ISO2 code: BG Country name : Bulgaria
 ISO2 code: SN Country name : Senegal
 ISO2 code: PT Country name : Portugal
 ISO2 code: ML Country name : Mali
 ISO2 code: MP Country name : Northern Mariana Islands
 ISO2 code: SZ Country name : Swaziland
 ISO2 code: BI Country name : Burundi
 ISO2 code: GM Country name : Gambia
 ISO2 code: PR Country name : Puerto Rico
 ISO2 code: FK Country name : Falkland Islands
 ISO2 code: CN Country name : China
 ISO2 code: KY Country name : Cayman Islands
 ISO2 code: TK Country name : Tokelau
 ISO2 code: HK Country name : Hong Kong
 ISO2 code: SO Country name : Somalia
 ISO2 code: EG Country name : Egypt
 ISO2 code: US Country name : United States
 ISO2 code: PN Country name : Pitcairn
 ISO2 code: VC Country name : Saint Vincent and the Grenadines
 ISO2 code: BQ Country name : Bonaire, Saint Eustatius and Saba
 ISO2 code: MK Country name : Macedonia
 ISO2 code: TV Country name : Tuvalu
 ISO2 code: RE Country name : Reunion
 ISO2 code: FR Country name : France
 ISO2 code: CX Country name : Christmas Island
 ISO2 code: KP Country name : North Korea
 ISO2 code: DO Country name : Dominican Republic
 ISO2 code: TW Country name : Taiwan
 ISO2 code: IS Country name : Iceland
 ISO2 code: GT Country name : Guatemala
 ISO2 code: PE Country name : Peru
 ISO2 code: FM Country name : Micronesia
 ISO2 code: IN Country name : India
 ISO2 code: SG Country name : Singapore
 ISO2 code: MZ Country name : Mozambique
 ISO2 code: BT Country name : Bhutan
 ISO2 code: GP Country name : Guadeloupe
 ISO2 code: MY Country name : Malaysia
 ISO2 code: BM Country name : Bermuda
 ISO2 code: AI Country name : Anguilla
 ISO2 code: QA Country name : Qatar
 ISO2 code: SS Country name : South Sudan
 ISO2 code: WS Country name : Samoa
 ISO2 code: HN Country name : Honduras
 ISO2 code: VU Country name : Vanuatu
 ISO2 code: FO Country name : Faroe Islands
 ISO2 code: TR Country name : Turkey
 ISO2 code: BH Country name : Bahrain
 ISO2 code: BS Country name : Bahamas
 ISO2 code: FJ Country name : Fiji
 ISO2 code: MS Country name : Montserrat
 ISO2 code: CH Country name : Switzerland
 ISO2 code: AD Country name : Andorra
 ISO2 code: GA Country name : Gabon
 ISO2 code: EC Country name : Ecuador
 ISO2 code: MA Country name : Morocco
 ISO2 code: MM Country name : Myanmar
 ISO2 code: TZ Country name : Tanzania
 ISO2 code: SH Country name : Saint Helena
 ISO2 code: SX Country name : Sint Maarten
 ISO2 code: LA Country name : Laos
 ISO2 code: BL Country name : Saint Barthelemy
 ISO2 code: RS Country name : Serbia
 ISO2 code: MG Country name : Madagascar
 ISO2 code: AQ Country name : Antarctica
 ISO2 code: BZ Country name : Belize
 ISO2 code: ZW Country name : Zimbabwe
 ISO2 code: KH Country name : Cambodia
 ISO2 code: GD Country name : Grenada
 ISO2 code: AM Country name : Armenia
 ISO2 code: GW Country name : Guinea-Bissau
 ISO2 code: NO Country name : Norway
 ISO2 code: PH Country name : Philippines
 ISO2 code: AR Country name : Argentina
 ISO2 code: BV Country name : Bouvet Island
 ISO2 code: ER Country name : Eritrea
 ISO2 code: DK Country name : Denmark
 ISO2 code: BB Country name : Barbados
 ISO2 code: SA Country name : Saudi Arabia
 ISO2 code: NA Country name : Namibia
 ISO2 code: UY Country name : Uruguay
 ISO2 code: TT Country name : Trinidad and Tobago
 ISO2 code: AO Country name : Angola
 ISO2 code: IL Country name : Israel
 ISO2 code: KM Country name : Comoros
 ISO2 code: KZ Country name : Kazakhstan
 ISO2 code: JP Country name : Japan
 ISO2 code: IQ Country name : Iraq
 ISO2 code: VN Country name : Vietnam
 ISO2 code: SB Country name : Solomon Islands
 ISO2 code: MH Country name : Marshall Islands
 ISO2 code: CZ Country name : Czech Republic
 ISO2 code: KW Country name : Kuwait
 ISO2 code: SV Country name : El Salvador
 ISO2 code: PM Country name : Saint Pierre and Miquelon
 ISO2 code: IT Country name : Italy
 ISO2 code: HR Country name : Croatia
 ISO2 code: HT Country name : Haiti
 ISO2 code: MF Country name : Saint Martin
 ISO2 code: UZ Country name : Uzbekistan
 ISO2 code: CO Country name : Colombia
 ISO2 code: BR Country name : Brazil
 ISO2 code: GY Country name : Guyana
 ISO2 code: GL Country name : Greenland
 ISO2 code: VG Country name : British Virgin Islands
 ISO2 code: CU Country name : Cuba
 ISO2 code: ST Country name : Sao Tome and Principe
 ISO2 code: GG Country name : Guernsey
 ISO2 code: PF Country name : French Polynesia
 ISO2 code: ZA Country name : South Africa
 ISO2 code: FI Country name : Finland
 ISO2 code: YT Country name : Mayotte
 ISO2 code: TO Country name : Tonga
 ISO2 code: AG Country name : Antigua and Barbuda
 ISO2 code: JE Country name : Jersey
 ISO2 code: RU Country name : Russia
 ISO2 code: MQ Country name : Martinique
 ISO2 code: NZ Country name : New Zealand
 ISO2 code: ES Country name : Spain
 ISO2 code: MW Country name : Malawi
 ISO2 code: MR Country name : Mauritania
 ISO2 code: ID Country name : Indonesia
 ISO2 code: PW Country name : Palau
 ISO2 code: MO Country name : Macao
 ISO2 code: LI Country name : Liechtenstein
 ISO2 code: MN Country name : Mongolia
 ISO2 code: NL Country name : Netherlands
 ISO2 code: CL Country name : Chile
 ISO2 code: KG Country name : Kyrgyzstan
 ISO2 code: SR Country name : Suriname
 ISO2 code: BO Country name : Bolivia
 ISO2 code: BJ Country name : Benin
 ISO2 code: SJ Country name : Svalbard and Jan Mayen
 ISO2 code: KI Country name : Kiribati
 ISO2 code: IE Country name : Ireland
 ISO2 code: GU Country name : Guam
 ISO2 code: KN Country name : Saint Kitts and Nevis
 ISO2 code: DJ Country name : Djibouti
 ISO2 code: XK Country name : Kosovo
 ISO2 code: AX Country name : Aland Islands
 ISO2 code: RW Country name : Rwanda
 ISO2 code: CM Country name : Cameroon
 ISO2 code: AF Country name : Afghanistan
 ISO2 code: MT Country name : Malta
 ISO2 code: CW Country name : Curacao
 ISO2 code: SI Country name : Slovenia
 ISO2 code: LK Country name : Sri Lanka
 ISO2 code: AS Country name : American Samoa
 ISO2 code: WF Country name : Wallis and Futuna
 ISO2 code: BW Country name : Botswana
 ISO2 code: MU Country name : Mauritius
 ISO2 code: SL Country name : Sierra Leone
 ISO2 code: LR Country name : Liberia
 ISO2 code: MV Country name : Maldives
 ISO2 code: DZ Country name : Algeria
 ISO2 code: UA Country name : Ukraine
 ISO2 code: BA Country name : Bosnia and Herzegovina
 ISO2 code: GF Country name : French Guiana
 ISO2 code: GN Country name : Guinea
 ISO2 code: AZ Country name : Azerbaijan
 ISO2 code: NR Country name : Nauru
 ISO2 code: KR Country name : South Korea
 ISO2 code: SM Country name : San Marino
 ISO2 code: SK Country name : Slovakia
 ISO2 code: GH Country name : Ghana
 ISO2 code: PY Country name : Paraguay
 ISO2 code: MD Country name : Moldova
 ISO2 code: SY Country name : Syria
 ISO2 code: GR Country name : Greece
 ISO2 code: NI Country name : Nicaragua
 ISO2 code: BY Country name : Belarus
 ISO2 code: TL Country name : East Timor
 ISO2 code: RO Country name : Romania
 ISO2 code: EE Country name : Estonia
 ISO2 code: NU Country name : Niue
 ISO2 code: DM Country name : Dominica
 ISO2 code: BN Country name : Brunei
 ISO2 code: TD Country name : Chad
 ISO2 code: ZM Country name : Zambia
 ISO2 code: LC Country name : Saint Lucia
 ISO2 code: ME Country name : Montenegro
 ISO2 code: CA Country name : Canada
 ISO2 code: KE Country name : Kenya
 ISO2 code: NP Country name : Nepal
 ISO2 code: CR Country name : Costa Rica
 ISO2 code: BE Country name : Belgium
 ISO2 code: VI Country name : U.S. Virgin Islands
 ISO2 code: IR Country name : Iran
 ISO2 code: LB Country name : Lebanon
 ISO2 code: AE Country name : United Arab Emirates
 ISO2 code: VE Country name : Venezuela
 ISO2 code: UG Country name : Uganda
 ISO2 code: OM Country name : Oman
 ISO2 code: CF Country name : Central African Republic
 ISO2 code: UM Country name : United States Minor Outlying Islands
 ISO2 code: GQ Country name : Equatorial Guinea
 ISO2 code: GB Country name : United Kingdom
 ISO2 code: GI Country name : Gibraltar
 ISO2 code: GE Country name : Georgia
 ISO2 code: CI Country name : Ivory Coast
 ISO2 code: TF Country name : French Southern Territories
 ISO2 code: IM Country name : Isle of Man
 ISO2 code: MX Country name : Mexico
 ISO2 code: NF Country name : Norfolk Island
 ISO2 code: CV Country name : Cape Verde
 ISO2 code: TJ Country name : Tajikistan
 ISO2 code: PS Country name : Palestinian Territory
 ISO2 code: ET Country name : Ethiopia
 ISO2 code: BF Country name : Burkina Faso
 ISO2 code: HU Country name : Hungary
 ISO2 code: LY Country name : Libya
 ISO2 code: BD Country name : Bangladesh
 ISO2 code: JO Country name : Jordan
 ISO2 code: CG Country name : Republic of the Congo
 ISO2 code: CD Country name : Democratic Republic of the Congo
 ISO2 code: SE Country name : Sweden
 ISO2 code: DE Country name : Germany
 ISO2 code: LV Country name : Latvia
 ISO2 code: JM Country name : Jamaica
 ISO2 code: TM Country name : Turkmenistan
 ISO2 code: HM Country name : Heard Island and McDonald Islands
 ISO2 code: NE Country name : Niger
 ISO2 code: AT Country name : Austria
 ISO2 code: EH Country name : Western Sahara
 ISO2 code: CY Country name : Cyprus
 ISO2 code: PG Country name : Papua New Guinea
 ISO2 code: IO Country name : British Indian Ocean Territory
 ISO2 code: CK Country name : Cook Islands
 ISO2 code: NC Country name : New Caledonia
 ISO2 code: SC Country name : Seychelles
 ISO2 code: AU Country name : Australia
 ISO2 code: LS Country name : Lesotho
 ISO2 code: TG Country name : Togo
 ISO2 code: GS Country name : South Georgia and the South Sandwich Islands
 ISO2 code: NG Country name : Nigeria
 ISO2 code: CC Country name : Cocos Islands

References :

https://www.socketloop.com/tutorials/golang-decode-unmarshal-unknown-json-data-type-with-map-string-interface

http://country.io