This will return the distance between two points in miles.
To get the distance in kilometers, multiply with `1.60934`

.

```
func distance(lat1 float64, lng1 float64, lat2 float64, lng2 float64) float64 {
radlat1 := float64(math.Pi * lat1 / 180)
radlat2 := float64(math.Pi * lat2 / 180)
theta := float64(lng1 - lng2)
radtheta := float64(math.Pi * theta / 180)
dist := math.Sin(radlat1)*math.Sin(radlat2) + math.Cos(radlat1)*math.Cos(radlat2)*math.Cos(radtheta)
if dist > 1 {
dist = 1
}
dist = math.Acos(dist)
dist = dist * 180 / math.Pi
dist = dist * 60 * 1.1515
return dist
}
```