First part of the solution.

03082020-Githawk-1-solution.swift

override func fetch(page: String?) {
    
    // Protect your inputs.
    let requestedPage: Int
    if let givenPageString = page,
        let givenPageInt = Int(givenPageString)  {
        requestedPage = givenPageInt
    } else {
        requestedPage = 1
    }
    
    fetch(owner: owner, repo: repo, pageNumber: requestedPage) { result in
        
        switch result {
            
        case .success(let success):
            
            let firstPageRequested = (page == nil)
            if firstPageRequested {
                self.users = success.asignees
            } else {
                self.users += success.asignees
            }
            
            if let nextPage = success.nextPage {
                self.update(page: "\(nextPage)", animated: true)
            } else {
                self.update(animated: true)
            }
            
        case .error(let possibleError):
            Squawk.show(error: possibleError)
        }
    }
}