This set of functions allows interacting with the HostIP JSON API from Go.

jsonapi.go

package main

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

// This is our type which matches the JSON object.
type IpRecord struct {
	// These two fields use the json: tag to specify which field they map to
	CountryName string `json:"country_name"`
	CountryCode string `json:"country_code"`
	// These fields are mapped directly by name (note the different case)
	City string
	Ip   string
	// As these fields can be nullable, we use a pointer to a string rather than a string
	Lat *string
	Lng *string
}

func main() {
	// Note this example requires fmt in the list of imports
	record, _ := GetIpRecord("198.252.206.16")
	fmt.Printf("stackoverflow.com information:\n%v\n", record)
	record, _ = GetIpRecord("184.72.186.1")
	fmt.Printf("hostip.info information:\n%v\n", record)
	record, _ = GetIpRecord("108.162.195.222")
	fmt.Printf("codingcookies.com information:\n%v\n", record)
}

// This function fetch the content of a URL will return it as an
// array of bytes if retrieved successfully.
func getContent(url string) ([]byte, error) {
	// Build the request
	req, err := http.NewRequest("GET", url, nil)
	if err != nil {
		return nil, err
	}
	// Send the request via a client
	client := &http.Client{}
	resp, err := client.Do(req)
	if err != nil {
		return nil, err
	}
	// Defer the closing of the body
	defer resp.Body.Close()
	// Read the content into a byte array
	body, err := ioutil.ReadAll(resp.Body)
	if err != nil {
		return nil, err
	}
	// At this point we're done - simply return the bytes
	return body, nil
}

// This function will attempt to get the IP record for
// a given IP. If no errors occur, it will return a pair
// of the record and nil. If it was not successful, it will
// return a pair of nil and the error.
func GetIpRecord(ip string) (*IpRecord, error) {
	// Fetch the JSON content for that given IP
	content, err := getContent(
		fmt.Sprintf("http://api.hostip.info/get_json.php?position=true&ip=%s", ip))
	if err != nil {
		// An error occurred while fetching the JSON
		return nil, err
	}
	// Fill the record with the data from the JSON
	var record IpRecord
	err = json.Unmarshal(content, &record)
	if err != nil {
		// An error occurred while converting our JSON to an object
		return nil, err
	}
	return &record, err
}