waiting until URLSession.shared.dataTask ends - swiftui

Question

I have the below code. I got print "OK Call" before to print (finalData). I know the reason is URLSession goes in parallel, but my question is: How could avoid the parallel task and wait until URLSession ends ? THANKS
import SwiftUI
struct ContentView: View {
var body: some View {
Button ("Action", action: {
self.checkLogin(username:"test", password:"123456")
print ("OK Call")
} ) }
func checkLogin (username: String, password: String) {
var body: [String:String] = [:]
guard let url = URL(string: "http://test/apple/login.php") else { return }
body = ["user": username, "password": password]
let finalBody = try! JSONEncoder().encode (body)
var request = URLRequest(url: url)
request.httpMethod = "POST"
request.httpBody = finalBody
request.setValue("application/json", forHTTPHeaderField: "Content-Type")
URLSession.shared.dataTask(with: request) { (data,response,error) in
if let error = error { print ("Error: \(error)")
return
}
if let data = data {
let finalData = try! JSONDecoder().decode(ServerMessage.self, from: data)
print (finalData)
return
}
}.resume()
}
}
struct ServerMessage: Decodable {
let result: String
let nuser: String
}