URLSessionConfiguration.background() method marked as unavailable since it only supported by Darwin infrastructure.

Author: karthikkeyan

Foundation/URLSession/URLSessionConfiguration.swift

@@ -156,17 +156,8 @@ open class URLSessionConfiguration : NSObject, NSCopying {
         return ephemeralConfiguration
     }
 
-    open class func background(withIdentifier identifier: String) -> URLSessionConfiguration {
-        if identifier.isEmpty {
-            // As per document: The unique identifier for the configuration object. This parameter must not be nil or an empty string.
-            // But it is unclear what happens when it is empty, the existing Foundation framework creates an instance anyway.
-            // FIXME: Handle empty string properly
-        }
-        let backgroundConfiguration = URLSessionConfiguration.default.copy() as! URLSessionConfiguration
-        backgroundConfiguration.identifier = identifier
-        backgroundConfiguration.urlCache = nil
-        return backgroundConfiguration
-    }
+    @available(*, unavailable, message: "Not available on non-Darwin platforms")
+    open class func background(withIdentifier identifier: String) -> URLSessionConfiguration { NSUnsupported() }
 
     /* identifier for the background session configuration */
     open var identifier: String?