Detecting the location of users visiting your website is useful for a variety of reasons.

• You might want to display different content based on different languages for people from different countries OR
• Display targeted information to visitors from different locations OR
• You may have setup database shards and want user signups to go to appropriate database based on their geography

Whatever your reasons, this middleware comes to your rescue!

gin-geo uses the following Go packages as dependencies:

• github.com/gin-gonic/gin

Step 1: Assuming you've installed Go and Gin, run this command to get the middleware:

$ go get github.com/cjgiridhar/gin-geo

[OPTIONAL] Step 2: Download latest GeoLite2 City Database from Maxmind.

$ wget http://geolite.maxmind.com/download/geoip/database/GeoLite2-City.mmdb.gz
$ gunzip GeoLite2-City.mmdb.gz  

OR Copy it from the gin-geo repository

cp github.com/cjgiridhar/gin-geo/example/GeoLite2-City.mmdb .

[OPTIONAL] Step 3: Make sure file path for mmdb file is at correct location. Please place the file from where your program runs.

If you look at the gin-geo sample code, example.go is pointing to the database location from the package. Hence Step 2 and Step 3 are optional. If you need to use the latest database, please follow Step 2 and point the database path correctly.

main.go

package main

import (
	"net/http"

	geo "github.com/cjgiridhar/gin-geo"
	"github.com/gin-gonic/gin"
)

func main() {
	gin.SetMode(gin.ReleaseMode)
	r := gin.Default()
	r.Use(geo.Default("github.com/cjgiridhar/gin-geo/db/GeoLite2-City.mmdb"))
	r.GET("/geo", func(c *gin.Context) {
		geoResponse, ok := c.Get("GeoResponse")
		if ok {
			c.JSON(http.StatusOK, gin.H{
				"geo": geoResponse,
			})
		} else {
			c.AbortWithStatusJSON(http.StatusInternalServerError, gin.H{
				"detail": "Could not get geographical information",
			})
		}
	})
	r.Run()
}

You need a request from the internet to see the middleware in action. For this you will need a public URL for exposing your local web server.

Follow the steps:

• Create a main.go file and copy the contents as given in the Usage section.
• Make sure GeoLite2-City.mmdb is placed in the same path as main.go. [OPTIONAL]
• Run the demo as: go run main.go (This will run a local web server on port 8080).
• Download ngrok and run ./ngrok http 8080 (This will generate public URL and expose local web server to the internet).
• Browse the public URL obtained from step 2, say https://public.ngrok.io/geo, from your browser.

{
	"geo": {
		"IPAddress":"151.236.26.140",
		"CityName":"Zurich",
		"StateCode":"Zurich",
		"CountryCode":"CH",
		"ContinentCode":"EU",
		"TimeZone":"Europe/Zurich",
		"ZipCode":"8048",
		"Latitude":47.3667,
		"Longitude":8.55,
		"Language":"de",
	}
}

2020/03/18 09:54:36 Geo: Middleware duration 391.525µs
&{151.236.26.140 Zurich Zurich CH EU Europe/Zurich 8048 47.3667 8.55 de {0 }}
[GIN] 2020/03/18 - 09:54:36 | 200 |     472.715µs |    151.236.26.140 | GET      "/geo"

Based on the above sample output, you can use the CountryCode or ContinentCode information to make meaningful decisions for the client.

For instance, if it's a EU country, you can create the account for the client on a server hosted in EU region as per GDPR requirements.

This middleware uses Maxmind's GeoLite (https://www.maxmind.com/en/home) database to get geo information and used HTTP headers to get the IP Address and Language for the user.

Technobeans, https://technobeans.com