Merge pull request malcommac#80 from malcommac/bug/79-linux-compilati…

…on-error

Fixed compilation under Linux Environment

Sources/Hydra/Promise+Await.swift

@@ -92,17 +92,23 @@ public extension Context {
 	///  Awaits that the given promise fulfilled with its value or throws an error if the promise fails.
 	///
 	/// - Parameter promise: target promise
-	/// - Returns: return the value of the promise
-	/// - Throws: throw if promise fails
-	@discardableResult
-	internal func await<T>(_ promise: Promise<T>) throws -> T {
-		guard self.queue != DispatchQueue.main else {
-			// execute a promise on main context does not make sense
-			// dispatch_semaphore_wait should NOT be called on the main thread.
-			// more here: https://medium.com/@valentinkalchev/how-to-pause-and-resume-a-sequence-of-mutating-swift-structs-using-dispatch-semaphore-fc98eca55c0#.ipbujy4k2
-			throw PromiseError.invalidContext
-		}
-
+    /// - Returns: return the value of the promise
+    /// - Throws: throw if promise fails
+    @discardableResult
+    internal func await<T>(_ promise: Promise<T>) throws -> T {
+        #if os(Linux)
+        let isNotMainQueue = self.queue.label != DispatchQueue.main.label
+        #else
+        let isNotMainQueue = self.queue != DispatchQueue.main
+        #endif
+
+        guard isNotMainQueue else {
+            // execute a promise on main context does not make sense
+            // dispatch_semaphore_wait should NOT be called on the main thread.
+            // more here: https://medium.com/@valentinkalchev/how-to-pause-and-resume-a-sequence-of-mutating-swift-structs-using-dispatch-semaphore-fc98eca55c0#.ipbujy4k2
+            throw PromiseError.invalidContext
+        }
+
 		var result: T?
 		var error: Error?