Go loading data and coordinates from GeoJson file to PostgreSQL using Gorm.

main.go

package main

import (
	"flag"
	"fmt"
	"io/ioutil"
	"strconv"
	"time"

	geojson "github.com/paulmach/go.geojson"
	"gorm.io/driver/postgres"
	"gorm.io/gorm"
	"gorm.io/gorm/logger"
)

func main() {
	flag.Parse()
	rawFeatureJSON, err := ioutil.ReadFile(*file)
	if err != nil {
		panic(err)
	}
	fc, err := geojson.UnmarshalFeatureCollection(rawFeatureJSON)
	if err != nil {
		panic(err)
	}
	gormdb := open()
	for _, f := range fc.Features {
		fmt.Printf("Name: %v\n\n", f.Properties["name"])
		fmt.Printf("Type: %v\n\n", f.Geometry.Type)
		name := f.Properties["name"].(string)
		switch {
		case f.Geometry.Type == "Polygon":
			coor := polygonCoordinates(f.Geometry.Polygon)
			coor = fmt.Sprintf("POLYGON(%s)\n", coor)
			insert(gormdb, name, coor)
		case f.Geometry.Type == "GeometryCollection":
			coor := "MULTIPOLYGON("
			for i := range f.Geometry.Geometries {
				coor += "("
				coor += polygonCoordinates(f.Geometry.Geometries[i].Polygon)
				coor += "),"
			}
			coor = coor[:len(coor)-1]
			coor += ")"
			insert(gormdb, name, coor)
			break
		default:
			panic(f.Geometry.Type)
		}
	}
	fmt.Printf("List the items just inserted:\n")
	list(gormdb)
}

var dsn = flag.String("dsn", "", "PostgreSQL DSN")
var file = flag.String("file", "", ".geojson")

type Grid struct {
	Id        int64 `gorm:"primarykey"`
	CreatedAt time.Time
	UpdatedAt time.Time
	DeletedAt gorm.DeletedAt `gorm:"index"`
	Name      string
}

func open() (gormdb *gorm.DB) {
	gormdb, err := gorm.Open(postgres.Open(*dsn), &gorm.Config{
		Logger: logger.Default.LogMode(logger.Info),
	})
	if err != nil {
		panic(err)
	}
	gormdb.AutoMigrate(&Grid{})
	gormdb.Exec("ALTER TABLE grids ADD COLUMN IF NOT EXISTS geom geometry")
	gormdb.Exec("CREATE INDEX IF NOT EXISTS grids_idx_geom ON grids USING GIST(geom)")
	return
}

func insert(gormdb *gorm.DB, name, coor string) {
	grid := Grid{
		Name: name,
	}
	tx := gormdb.Begin()
	err := tx.Create(&grid).Error
	if err != nil {
		fmt.Printf("%s: %v\n", name, err)
		tx.Rollback()
		panic(err)
	}
	err = tx.Exec("UPDATE grids SET geom = '"+coor+"' WHERE id = ?", grid.Id).Error
	if err != nil {
		fmt.Printf("%s: %v\n", name, err)
		tx.Rollback()
		panic(err)
	}
	err = tx.Commit().Error
	if err != nil {
		fmt.Printf("%s: %v\n", name, err)
		panic(err)
	}
}

func list(gormdb *gorm.DB) {
	rows, err := gormdb.Table("grids").Select("id, name, ST_AsGeojson(geom) AS coordinates").Rows()
	if err != nil {
		panic(err)
	}
	defer rows.Close()
	for rows.Next() {
		var id int64
		var name, coordinates string
		rows.Scan(&id, &name, &coordinates)
		fmt.Printf("%d: %s: %s\n", id, name, coordinates)
	}
}

func polygonCoordinates(polygon [][][]float64) (coor string) {
	for i := range polygon {
		coor += "("
		for j := range polygon[i] {
			if len(polygon[i][j]) > 1 {
				long := strconv.FormatFloat(polygon[i][j][0], 'f', -1, 64)
				lat := strconv.FormatFloat(polygon[i][j][1], 'f', -1, 64)
				coor += long + " " + lat + ","
			}
		}
		coor = coor[:len(coor)-1]
		coor += "),"
	}
	coor = coor[:len(coor)-1]
	return
}