如何显示仅连接2个点的多段线?

我使用iOS谷歌地图API来显示地图。我想在特定的经度处添加一条线,这样用户就可以知道经度在哪里。

这就是我所尝试的:

let path = GMSMutablePath()
path.add(CLLocationCoordinate2D(latitude: -90, longitude: -122))
path.add(CLLocationCoordinate2D(latitude: 90, longitude: -122))
polyline = GMSPolyline(path: path)
polyline.geodesic = true
polyline.strokeColor = .red
polyline.strokeWidth = 20 // I have set this to a big number to guarantee that my poor eyesight can see the line
polyline.map = mapView

我在任何地方都看不到这条线!

作为一个控制实验,我复制了从 tutorial 并将其粘贴在上述代码之后:

let rect = GMSMutablePath()
rect.add(CLLocationCoordinate2D(latitude: 37.36, longitude: -122.0))
rect.add(CLLocationCoordinate2D(latitude: 37.45, longitude: -122.0))
rect.add(CLLocationCoordinate2D(latitude: 37.45, longitude: -122.2))
rect.add(CLLocationCoordinate2D(latitude: 37.36, longitude: -122.2))

// Create the polygon, and assign it to the map.
let polygon = GMSPolygon(path: rect)
polygon.fillColor = UIColor(red: 0.25, green: 0, blue: 0, alpha: 0.2);
polygon.strokeColor = .black
polygon.strokeWidth = 2
polygon.map = mapView

它显示了矩形:

因为我画线的代码就在画矩形的代码的正上方,所以我的代码也应该被执行。它应该画一条与矩形相接触的线,从北极延伸到南极。但为什么没有这样的界线呢?