Swift Multiplatform Experiments. Read comments below.

universalTest.swift

import Foundation

// needed for Linux
#if canImport(FoundationNetworking)
    import FoundationNetworking
#endif

// New async await URLSession extensions are available solely on Apple platform
// so this polyfill it's necessary, otherwise the code does not compile on Linux
extension URLSession {
    func universalData(for request: URLRequest) async throws -> (Data, URLResponse?) {
        #if canImport(FoundationNetworking)
            print("On Linux")
            return await withCheckedContinuation { continuation in
                URLSession.shared.dataTask(with: request) { data, response, _ in
                    guard let data = data else {
                        fatalError()
                    }
                    continuation.resume(returning: (data, response))
                }.resume()
            }
        #else
            print("On macOS")
            return try await URLSession.shared.data(for: request)
        #endif
    }
}

struct Dog: Codable {
    let message: String
    let status: String

    var url: URL { URL(string: message)! }
}

func fetchDog() async throws -> Dog {
    let dogURL = URL(string: "https://dog.ceo/api/breeds/image/random")!
    let request = URLRequest(url: dogURL)
    let (data, _) = try await URLSession.shared.universalData(for: request)
    return try JSONDecoder().decode(Dog.self, from: data)
}

do {
    print(try await fetchDog())
} catch {
    print(error)
    print("ouch")
}

It runs successfully on:

• Intel Core i9 MacBookPro running macOS Ventura 13.0.1 and Xcode 14.1.0
• Raspberry Pi 2 running Raspbian Bullseye 11 and Swift built for ARM installed with (select the first option, to get latest available swift):

  curl -s https://archive.swiftlang.xyz/install.sh | sudo bash
  sudo apt install swiftlang
  

Useful Article about Swift Concurrency on Linux