Fix Linux networking

Sources/Push/PushClient.swift

@@ -145,41 +145,12 @@ public final class PushClient {
         var request = URLRequest(url: server.appendingPathComponent(route.rawValue))
         request.httpBody = bodyData
         request.httpMethod = "POST"
-
-        if #available(iOS 15.0, *) {
         return await post(request)
-        } else {
-            return await withCheckedContinuation { continuation in
-                postRequest(request) { data in
-                    continuation.resume(returning: data)
-                }
-            }
-        }
     }
 
-    private func postRequest(_ request: URLRequest, completion: @escaping (Data?) -> Void) {
-        URLSession.shared.dataTask(with: request) { data, response, error in
-            if let error = error {
-                print("Failed with error: \(error)")
-                completion(nil)
-            }
-            guard let httpResponse = response as? HTTPURLResponse else {
-                completion(nil)
-                return
-            }
-            guard httpResponse.statusCode == 200 else {
-                print("Failed with code: \(httpResponse.statusCode)")
-                completion(nil)
-                return
-            }
-            completion(data)
-        }.resume()
-    }
-
-    @available(iOS 15.0, *)
     private func post(_ request: URLRequest) async -> Data? {
         do {
-            let (data, response) : (Data, URLResponse) = 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
             }
@@ -194,8 +165,37 @@ public final class PushClient {
         }
     }
 
+    private func data(for request: URLRequest) async throws -> (Data, URLResponse) {
+#if !canImport(FoundationNetworking)
+        if #available(iOS 15.0, *) {
+            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()
+        }
+    }
+}