title: Alamofire background fetch doesn't process fruther requests
body: <p>I'd like to perform a background fetch with <code>performFetchWithCompletionHandler</code>, obviously all previous solutions didn't worked for me.</p>
  
  <p>The weird thing is my first request are ok, but the next ones aren't.</p>
  
  <p>I tried to use a singleton of SessionManager, I also tried to dequeue all Alamofire requests to a background thread, and changed the <code>URLSessionManager</code> with <code>URLSessionConfiguration.background(withIdentifier: "com.test.background")</code>.</p>
  
  <pre class="lang-swift prettyprint-override"><code> group.enter()
   api.getClimateStateData(carId: carId, completion: { [weak self] response in
         guard let strongSelf = self else { return }
         climateModel = strongSelf.sortDataFromError(data: response)
         group.leave()
  })
  </code></pre>
  
  <pre class="lang-swift prettyprint-override"><code>func getClimateStateData(carId: Int, completion: @escaping (ServiceResponse&lt;ClimateStateModel&gt;) -&gt; Void) {
          let header: HTTPHeaders = ["User-Agent": UserAgentHelper.fullUserAgentString]
          request("/api/1/vehicles/\(carId)/data_request/climate_state", method: .get, parameters: nil, encoding: nil, headers: header).responseData { [weak self] response in
              guard let strongSelf = self else { return }
              completion(strongSelf.completionResponse(response))
       }
  }
  </code></pre>
  
  <pre class="lang-swift prettyprint-override"><code>    @discardableResult private func request(
          _ path: String,
          method: HTTPMethod,
          parameters: Parameters? = nil,
          encoding: ParameterEncoding? = nil,
          headers: HTTPHeaders? = nil)
          -&gt; DataRequest {
              let userEncoding = encoding ?? self.defaultEncoding
              print("Asking: " + path)
              return Service.sessionManager2.request("\(API)\(path)", method: method, parameters: parameters, encoding: userEncoding, headers: headers).validate()
  }
  </code></pre>
  
  <p>I'd like to have those requests fulfilled.</p>
  
  <p>Thanks for the time!</p>