title: Alamofire custom parameters
body: <p>I am trying to convert this curl call to Alamofire in Swift.</p>
  
  <pre><code> curl -X POST https://content.dropboxapi.com/2/files/download    
       --header "Authorization: Bearer ab-xxx-x-x"     
       --header "Dropbox-API-Arg: {\"path\": "/acme101/acmeX100/acmeX100.001.png\"}"
  </code></pre>
  
  <p>And I figured this ...</p>
  
  <pre><code>let headers:HTTPHeaders = ["Authorization": "Bearer " + token2Save]
  let moreheaders:Parameters = ["Dropbox-API-Arg": ["path":sourcePath]]
  
  Alamofire.request("https://content.dropboxapi.com/2/files/download", parameters: moreheaders, encoding: URLEncoding(destination: .queryString), headers: headers).responseJSON { feedback in
          guard feedback.result.value != nil else {
              print("Error: did not receive data", print("request \(request) feedback \(feedback)"))
              return
          }
  </code></pre>
  
  <p>But of course it doesn't work, it crashes with ...</p>
  
  <pre><code>request (Function) feedback FAILURE: responseSerializationFailed(Alamofire.AFError.ResponseSerializationFailureReason.jsonSerializationFailed(Error Domain=NSCocoaErrorDomain Code=3840 "Invalid value around character 0." UserInfo={NSDebugDescription=Invalid value around character 0.}))
  Error: did not receive data ()
  </code></pre>
  
  <p>This needs to be in the header, not the body.</p>