How to calculate the distance between two longitudes and latitudes in Go language

package main
      
import (
    "fmt"
    "math"
)
      
func main() {
    lat1 := 29.490295
    lng1 := 106.486654
      
    lat2 := 29.615467
    lng2 := 106.581515
    (EarthDistance(lat1, lng1, lat2, lng2))
}
      
func EarthDistance(lat1, lng1, lat2, lng2 float64) float64 {
    radius := 6371000 // 6378137
    rad := /180.0
          
    lat1 = lat1 * rad
    lng1 = lng1 * rad
    lat2 = lat2 * rad
    lng2 = lng2 * rad
          
    theta := lng2 - lng1
    dist := ((lat1) * (lat2) + (lat1) * (lat2) * (theta))
          
    return dist * radius
}