SwiftyStoreKit example as function with return

Question

This example code from SwiftyStoreKit works, but I would like to convert it to a method that returns priceString.

SwiftyStoreKit.retrieveProductsInfo([productID]) { result in
            if let product = result.retrievedProducts.first {
                let priceString = product.localizedPrice!
                print("Product: \(product.localizedDescription), price: \(priceString)")
            }
            
            else if let invalidProductId = result.invalidProductIDs.first {
                print("Invalid product identifier: \(invalidProductId)")
            }
            else {
                print("Error: \(String(describing: result.error))")
            }
        }
    }

When I try this :

func getProductsTest() -> String {
        
        SwiftyStoreKit.retrieveProductsInfo([productID]) { result in
            if let product = result.retrievedProducts.first {
                let priceString = product.localizedPrice!
                print("Product: \(product.localizedDescription), price: \(priceString)")
            }
            
            else if let invalidProductId = result.invalidProductIDs.first {
                print("Invalid product identifier: \(invalidProductId)")
            }
            else {
                print("Error: \(String(describing: result.error))")
            }
        }
    }

I get the error "Cannot convert return expression of type 'InAppRequest' to return type 'String' Any idea how I can return the value of priceString?

Thanks