Bump iOS version

Package.swift

@@ -1,4 +1,4 @@
-// swift-tools-version: 5.5
+// swift-tools-version: 5.6
 
 import PackageDescription
 
@@ -14,8 +14,8 @@ let package = Package(
             targets: ["Push"]),
     ],
     dependencies: [
-        .package(url: "https://christophhagen.de/git/ch/Push-Definitions.git", from: "1.0.0"),
-        .package(url: "https://github.com/swift-server-community/APNSwift.git", from: "4.0.0"),
+        .package(url: "https://christophhagen.de/git/ch/Push-Definitions.git", from: "2.0.0-alpha.2"),
+        .package(url: "https://github.com/swift-server-community/APNSwift.git", from: "5.0.0-alpha.4"),
         .package(url: "https://github.com/apple/swift-crypto.git", "1.0.0" ..< "3.0.0")
     ],
     targets: [

Sources/Push/PushClient.swift

@@ -1,12 +1,18 @@
 import Foundation
 import PushMessageDefinitions
 
+// Use crypto replacement on Linux
 #if canImport(CryptoKit)
 import CryptoKit
 #else
 import Crypto
 #endif
 
+// Import network types on Linux
+#if canImport(FoundationNetworking)
+import FoundationNetworking
+#endif
+
 /**
  A client to interact with a push server.
  */
@@ -139,8 +145,12 @@ public final class PushClient {
         var request = URLRequest(url: server.appendingPathComponent(route.rawValue))
         request.httpBody = bodyData
         request.httpMethod = "POST"
+        return await post(request)
+    }
+
+    private func post(_ request: URLRequest) async -> Data? {
         do {
-            let (data, response) = try await URLSession.shared.data(for: request)
+            let (data, response) : (Data, URLResponse) = try await data(for: request)
             guard let httpResponse = response as? HTTPURLResponse else {
                 return nil
             }
@@ -155,8 +165,37 @@ public final class PushClient {
         }
     }
 
+    private func data(for request: URLRequest) async throws -> (Data, URLResponse) {
+#if !canImport(FoundationNetworking)
+        if #available(iOS 15.0, macOS 12.0, *) {
+            return try await URLSession.shared.data(for: request)
+        }
+#endif
+        return try await URLSession.shared.dataRequest(request)
+    }
+
     private func hash(_ masterKey: String) -> Data {
         Data(SHA256.hash(data: masterKey.data(using: .utf8)!))
     }
 
 }
+
+private extension URLSession {
+
+    func dataRequest(_ request: URLRequest) async throws -> (Data, URLResponse) {
+        try await withCheckedThrowingContinuation { continuation in
+            dataTask(with: request) { data, response, error in
+                if let error = error {
+                    print("Failed with error: \(error)")
+                    continuation.resume(throwing: error)
+                    return
+                }
+                guard let data = data, let response = response else {
+                    continuation.resume(throwing: URLError(.unknown))
+                    return
+                }
+                continuation.resume(returning: (data, response))
+            }.resume()
+        }
+    }
+}