fix(google-sign-in): dispatch sign-in UI presentation to main thread (#808)

* fix(google-sign-in): dispatch sign-in UI presentation to main thread

* fix(google-sign-in): move view controller access to main thread

Author: robingenz

.changeset/forty-mangos-feel.md

@@ -0,0 +1,5 @@
+---
+'@capawesome/capacitor-google-sign-in': patch
+---
+
+fix(ios): dispatch sign-in UI presentation to main thread

packages/google-sign-in/ios/Plugin/GoogleSignIn.swift

@@ -22,11 +22,6 @@ import GoogleSignIn
     }
 
     @objc public func signIn(completion: @escaping (_ result: SignInResult?, _ error: Error?) -> Void) {
-        guard let viewController = plugin.bridge?.viewController else {
-            completion(nil, CustomError.viewControllerUnavailable)
-            return
-        }
-
         let signInCompletion: (GIDSignInResult?, Error?) -> Void = { result, error in
             if let error = error {
                 if (error as NSError).code == GIDSignInError.canceled.rawValue {
@@ -76,10 +71,16 @@ import GoogleSignIn
             completion(signInResult, nil)
         }
 
-        if let scopes = self.scopes, !scopes.isEmpty {
-            GIDSignIn.sharedInstance.signIn(withPresenting: viewController, hint: nil, additionalScopes: scopes, completion: signInCompletion)
-        } else {
-            GIDSignIn.sharedInstance.signIn(withPresenting: viewController, completion: signInCompletion)
+        DispatchQueue.main.async {
+            guard let viewController = self.plugin.bridge?.viewController else {
+                completion(nil, CustomError.viewControllerUnavailable)
+                return
+            }
+            if let scopes = self.scopes, !scopes.isEmpty {
+                GIDSignIn.sharedInstance.signIn(withPresenting: viewController, hint: nil, additionalScopes: scopes, completion: signInCompletion)
+            } else {
+                GIDSignIn.sharedInstance.signIn(withPresenting: viewController, completion: signInCompletion)
+            }
         }
     }