Google Maps API: Adding letters to my markers on my google map

package main

import (
    "fmt"
    "log"
    "net/http"

    "github.com/gin-gonic/gin"
    "github.com/kr/pretty"
    "googlemaps.github.io/maps"
)

func main() {
    router := gin.Default()

    router.GET("/map", func(c *gin.Context) {
        apiKey := "YOUR_GOOGLE_MAPS_API_KEY"
        client, err := maps.NewClient(maps.WithAPIKey(apiKey))
        if err != nil {
            log.Fatal("Error creating Google Maps client: ", err)
        }

        locations := []maps.LatLng{
            {Lat: 37.7749, Lng: -122.4194},
            {Lat: 34.0522, Lng: -118.2437},
            {Lat: 40.7128, Lng: -74.0060},
        }

        markers := make([]maps.Marker, len(locations))
        for i, loc := range locations {
            markers[i] = maps.Marker{
                Position: loc,
                Label:    fmt.Sprintf("%c", 'A'+i), // Adding letters to markers
            }
        }

        mapURL := getMapURL(client, markers)

        c.JSON(http.StatusOK, gin.H{"map_url": mapURL})
    })

    router.Run(":8080")
}

func getMapURL(client *maps.Client, markers []maps.Marker) string {
    r := &maps.DirectionsRequest{
        Origin:      "San Francisco, CA",
        Destination: "Los Angeles, CA",
        Mode:        maps.TravelModeDriving,
        Waypoints:   markersToWaypoints(markers),
    }

    resp, _, err := client.Directions(nil, r)
    if err != nil {
        log.Fatal("Error getting directions: ", err)
    }

    pretty.Println(resp) // Displaying directions response for debugging (optional)

    mapURL := getStaticMapURL(resp.Routes[0].OverviewPolyline.Points, markers)
    return mapURL
}

func markersToWaypoints(markers []maps.Marker) []string {
    var waypoints []string
    for _, marker := range markers {
        waypoints = append(waypoints, marker.Position.String())
    }
    return waypoints
}

func getStaticMapURL(polyline string, markers []maps.Marker) string {
    var markerLabels string
    for _, marker := range markers {
        markerLabels += fmt.Sprintf("%c", 'A'+len(markerLabels))
    }

    return fmt.Sprintf("https://maps.googleapis.com/maps/api/staticmap?size=600x400&path=enc:%s&markers=label:%s", polyline, markerLabels)
}