PhotoStore is nil. Please help!

I was following the webservices chapter exactly as it mentioned but my PhotoStore is returned as nil.

Thread 1: Fatal error: Unexpectedly found nil while implicitly unwrapping an Optional value

This is my viewdidload() in PhotosViewController
`class PhotosViewController: UIViewController {

@IBOutlet var imageView: UIImageView!
var photoStore: PhotoStore!

override func viewDidLoad() {
    super.viewDidLoad()
    
    photoStore.fetchInterestingPhotos()
}

}`

Here is the PhotoStore.swift file
class PhotoStore {
private let session: URLSession = {
let config = URLSessionConfiguration.default
return URLSession(configuration: config)
}()

func fetchInterestingPhotos() {

    let url = FlickrAPI.interestingPhotosUrl
    let request = URLRequest(url: url)
    let task = session.dataTask(with: request) {
        (data, response, error) -> Void in

        if let jsonData = data {
            if let jsonString = String(data: jsonData,
                                       encoding: .utf8) {
                print(jsonString)
            }
        } else if let requestError = error {
            print("Error fetching interesting photos: \(requestError)")
        } else {
            print("Unexpected error with the request")
        }
    }
    task.resume()
}

}