Pull to refresh機能を付けたい

前提・実現したいこと

ここに質問の内容を詳しく書いてください。
リフレッシュ機能でニュースの更新をしたい。https://www.yururiwork.net/%E3%80%90swiftui%E3%80%91pull-to-refresh%EF%BC%88uirefreshcontrol%EF%BC%89%E3%82%92%E5%AE%9F%E8%A3%85%E3%81%99%E3%82%8B/
を参考にしてやってみたが、うまく行きません。

該当のソースコード

import SwiftUI
import SwiftyJSON
import SDWebImageSwiftUI
import WebKit

struct ContentView: View {

    @ObservedObject var list = getData()

    var body: some View {

        NavigationView{
            ZStack {
                RefreshControl(coordinateSpaceName: "RefreshControl", onRefresh: {
                                print("doRefresh()")
                            })

            List(list.datas){i in

               NavigationLink(destination:

                webView(url: i.url)
                    .navigationBarTitle("",displayMode: .inline)){
                
                

                    HStack(spacing: 15){

                        VStack(alignment: .leading, spacing: 10){

                            Text(i.title).fontWeight(.heavy)
                            Text(i.desc).lineLimit(2)
                        }


                    if i.image  != ""{
                        WebImage(url: URL(string: i.image)!, options: .highPriority,
                             context: nil)
                        .resizable()
                        .frame(width: 110, height: 135)
                        .cornerRadius(20)
                    }
                }.padding(.vertical, 15)
              }
            }.navigationBarTitle("Headlines")
        }
    }.coordinateSpace(name: "RefreshControl")
  }
    
}
struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}

struct dataType : Identifiable {

    var id : String
    var title : String
    var desc : String
    var url : String
    var image : String

}

class getData : ObservableObject{

    @Published var datas = [dataType]()

    init() {

        let source = "https://newsapi.org/v2/top-headlines?articles&country=jp&apiKey="

        let url = URL(string: source)!

        let session = URLSession(configuration: .default)

        session.dataTask(with: url) { (data, _, err) in

            if err != nil{
                print((err?.localizedDescription)!)
                return
            }

            let json = try! JSON(data: data!)

            for i in json["articles"]{

                let title = i.1["title"].stringValue
                let description = i.1["description"].stringValue
                let url = i.1["url"].stringValue
                let image = i.1["urlToImage"].stringValue
                let id = i.1["publishedAt"].stringValue
                DispatchQueue.main.async {

                    self.datas.append(dataType(id: id, title: title, desc: description, url:url, image: image ))

                }
            }


        }.resume()

      }

}
    struct webView : UIViewRepresentable {

        var url: String

        func makeUIView(context: UIViewRepresentableContext<webView>)->WKWebView{

            let view = WKWebView()
            view.load(URLRequest(url: URL(string:  url)!))
            return view
        }

            func updateUIView(_ uiView: WKWebView, context:
                                UIViewRepresentableContext<webView>) {

        }
}

struct RefreshControl: View {
    
    @State private var isRefreshing = false
    var coordinateSpaceName: String
    var onRefresh: () -> Void
    
    var body: some View {
        GeometryReader { geometry in
            if geometry.frame(in: .named(coordinateSpaceName)).midY > 50 {
                Spacer()
                    .onAppear() {
                        isRefreshing = true
                    }
            } else if geometry.frame(in: .named(coordinateSpaceName)).maxY < 10 {
                Spacer()
                    .onAppear() {
                        if isRefreshing {
                            isRefreshing = false
                            onRefresh()
                        }
                    }
            }
            HStack {
                Spacer()
                if isRefreshing {
                    ProgressView()
                } else {
                    Text("⬇︎")
                        .font(.system(size: 28))
                }
                Spacer()
            }
        }.padding(.top, -50)
    }
}