# Golang : How to calculate the distance between two coordinates using Haversine formula

I need to develop a service that calculate the distances of my current location to several points nearby. Each of the locations are represented by coordinates and my service will pick the 3 nearest points and select one of them. So, how to calculate the distances of my current location to each and every points?

Below is a simple example using the Haversine formula to calculate the distance between 2 coordinates.

Here you go!

```
package main
import (
"fmt"
"math"
)
type Coordinates struct {
Latitude float64
Longitude float64
}
const radius = 6371 // Earth's mean radius in kilometers
func degrees2radians(degrees float64) float64 {
return degrees * math.Pi / 180
}
func (origin Coordinates) Distance(destination Coordinates) float64 {
degreesLat := degrees2radians(destination.Latitude - origin.Latitude)
degreesLong := degrees2radians(destination.Longitude - origin.Longitude)
a := (math.Sin(degreesLat/2)*math.Sin(degreesLat/2) +
math.Cos(degrees2radians(origin.Latitude))*
math.Cos(degrees2radians(destination.Latitude))*math.Sin(degreesLong/2)*
math.Sin(degreesLong/2))
c := 2 * math.Atan2(math.Sqrt(a), math.Sqrt(1-a))
d := radius * c
return d
}
func main() {
pointA := Coordinates{2.990353, 101.533913}
pointB := Coordinates{2.960148, 101.577888}
fmt.Println("Point A : ", pointA)
fmt.Println("Point B : ", pointB)
distance := pointA.Distance(pointB)
fmt.Printf("The distance from point A to point B is %.2f kilometers.\n", distance)
}
```

Sample output:

Point A : {2.990353 101.533913}

Point B : {2.960148 101.577888}

The distance from point A to point B is 5.93 kilometers.

References :

#### See also : Golang : Find location by IP address and display with Google Map

##### By Adam Ng(黃武俊)

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