get UGC and FIPS from lat/lng

shp.go

package main

import (
	"fmt"
	"log"

	"github.com/jonas-p/go-shp"
	geo "github.com/kellydunn/golang-geo"
)

func main() {
	u, d := getUGC(-104.8547, 38.9008)
	f := getFIPS(-104.8547, 38.9008)
	fmt.Println(u, d)
	fmt.Println(f)
}

func getUGC(lat, lng float64) (string, string) {
	shape, err := shp.Open("z_04ap17.shp")
	if err != nil {
		log.Fatal(err)
	}
	defer shape.Close()

	fields := shape.Fields()
	desiredPoint := geo.NewPoint(lat, lng)

	for shape.Next() {
		n, p := shape.Shape()

		poly, ok := p.(*shp.Polygon)
		if !ok {
			fmt.Println("Failed to type assert")
		}

		var pointArr = make([]*geo.Point, len(poly.Points))
		for i, point := range poly.Points {
			pointArr[i] = geo.NewPoint(point.X, point.Y)
		}

		geop := geo.NewPolygon(pointArr)
		if geop.Contains(desiredPoint) {
			var ugc, desc string
			for k, f := range fields {
				if f.String() == "STATE_ZONE" {
					ugc = shape.ReadAttribute(n, k)
				}
				if f.String() == "NAME" {
					desc = shape.ReadAttribute(n, k)
				}
			}
			return ugc, desc
		}
	}
	fmt.Println("didn't find it")
	return "", ""
}

func getFIPS(lat, lng float64) string {
	shape, err := shp.Open("c_11au16.shp")
	if err != nil {
		log.Fatal(err)
	}
	defer shape.Close()

	fields := shape.Fields()
	desiredPoint := geo.NewPoint(lat, lng)

	for shape.Next() {
		n, p := shape.Shape()

		poly, ok := p.(*shp.Polygon)
		if !ok {
			fmt.Println("Failed to type assert")
		}

		var pointArr = make([]*geo.Point, len(poly.Points))
		for i, point := range poly.Points {
			pointArr[i] = geo.NewPoint(point.X, point.Y)
		}

		geop := geo.NewPolygon(pointArr)
		if geop.Contains(desiredPoint) {
			var fips string
			for k, f := range fields {
				if f.String() == "FIPS" {
					fips = shape.ReadAttribute(n, k)
				}
			}
			return fips
		}
	}
	fmt.Println("didn't find it")
	return ""
}