NativeProgressView4.swift

import SwiftUI

struct ContentView: View {
    
    let timer = Timer.publish(every: 0.25, on: .main, in: .default).autoconnect()
    @State private var progress: CGFloat = 0.0
    var total: CGFloat = 1.0
    
    var body: some View {
        ProgressView(value: progress, total: total)
            .progressViewStyle(CustomLinearProgressViewStyle1(progress: progress, total: total))
            .padding(20)
            .onReceive(timer) { _ in
                if progress < 1 {
                    self.progress += 0.1
                } else {
                    timer.upstream.connect().cancel()
                }
            }
    }
    
}

struct CustomLinearProgressViewStyle1: ProgressViewStyle {

    var progressColour: Color = .blue
    var successColour: Color = .green
    var progress: CGFloat
    var total: CGFloat
    
    func makeBody(configuration: Configuration) -> some View {
        ProgressView(configuration)
            .foregroundColor(progress >= total ? successColour : progressColour)
            .accentColor(progress >= total ? successColour : progressColour)
            .animation(Animation.linear(duration: 1))
    }
    
}

struct CustomLinearProgressViewStyle2: ProgressViewStyle {

    var progressColour: Color = .blue
    var successColour: Color = .green
    var progress: CGFloat
    var total: CGFloat
    
    func makeBody(configuration: Configuration) -> some View {
        ProgressView(configuration)
            .padding(.all, 10)
            .background(Color.black.opacity(0.1))
            .cornerRadius(10)
            .foregroundColor(progress >= total ? successColour : progressColour)
            .accentColor(progress >= total ? successColour : progressColour)
            .animation(Animation.linear(duration: 1))
    }
    
}