Use message to extension to obtain version info.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

WireGuard/ViewControllers/SetttingsTableViewController.swift

@@ -3,9 +3,15 @@
 //
 
 import UIKit
+import PromiseKit
+
+enum GoVersionError: Error {
+    case noDelegate
+}
 
 protocol SettingsTableViewControllerDelegate: class {
     func exportTunnels(settingsTableViewController: SettingsTableViewController, sourceView: UIView)
+    func goVersionInformation() -> Promise<String>
 }
 
 class SettingsTableViewController: UITableViewController {
@@ -21,14 +27,24 @@ class SettingsTableViewController: UITableViewController {
     override func viewDidLoad() {
         super.viewDidLoad()
         versionInfoLabel.text = versionInformation
-        goVersionInfoLabel.text = goVersionInformation
+        _ = firstly { () -> Promise<String> in
+            self.goVersionInfoLabel.text = NSLocalizedString("Loading...", comment: "")
+            return goVersionInformation()
+        }.then { (goVersion: String) -> Guarantee<Void> in
+            if let label = self.goVersionInfoLabel {
+                label.text = goVersion
+            }
+            return Guarantee.value(())
+            }.recover({ (_) in
+                self.goVersionInfoLabel.text = NSLocalizedString("Unknown", comment: "")
+            })
     }
 
     override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
         if let cell = tableView.cellForRow(at: indexPath) {
             switch cell {
             case versionInfoCell, goVersionInfoCell:
-                UIPasteboard.general.string = ["WireGuard for iOS:", versionInformation, "Go userspace backend:", goVersionInformation].joined(separator: "\n")
+                UIPasteboard.general.string = ["WireGuard for iOS:", versionInformation, "Go userspace backend:", goVersionInfoLabel.text ?? ""].joined(separator: "\n")
                 showCopyConfirmation()
             case exportCell:
                 delegate?.exportTunnels(settingsTableViewController: self, sourceView: exportCell)
@@ -49,8 +65,8 @@ class SettingsTableViewController: UITableViewController {
         return versionElements.joined(separator: " ")
     }
 
-    var goVersionInformation: String {
-        return wgVersion().flatMap { String(cString: $0) } ?? ""
+    func goVersionInformation() -> Promise<String> {
+        return self.delegate?.goVersionInformation() ?? Promise(error: GoVersionError.noDelegate)
     }
 
     private func showCopyConfirmation() {