Swift Google地图平滑圆角折线

pod 'GoogleMaps'

import GoogleMaps

func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
    GMSServices.provideAPIKey("YOUR_API_KEY")
    return true
}

import UIKit
import GoogleMaps

class ViewController: UIViewController {
    var mapView: GMSMapView!

    override func viewDidLoad() {
        super.viewDidLoad()
        let camera = GMSCameraPosition.camera(withLatitude: -33.86, longitude: 151.20, zoom: 6.0)
        mapView = GMSMapView.map(withFrame: self.view.frame, camera: camera)
        self.view.addSubview(mapView)
        
        drawSmoothPolyline()
    }
}

func drawSmoothPolyline() {
    let path = GMSMutablePath()
    let coordinates = [
        CLLocationCoordinate2D(latitude: -33.86, longitude: 151.20),
        CLLocationCoordinate2D(latitude: -33.70, longitude: 151.40),
        CLLocationCoordinate2D(latitude: -34.00, longitude: 151.20)
    ]
    
    for i in 0..<coordinates.count {
        if i == 0 {
            path.add(coordinates[i])
        } else {
            let previous = coordinates[i - 1]
            let current = coordinates[i]
            let midPoint = CLLocationCoordinate2D(latitude: (previous.latitude + current.latitude) / 2,
                                                  longitude: (previous.longitude + current.longitude) / 2)
            path.add(midPoint)
            path.add(current)
        }
    }
    
    let polyline = GMSPolyline(path: path)
    polyline.strokeWidth = 5.0
    polyline.map = mapView
}