code: func (buh *blobUploadHandler) CancelBlobUpload(w http.ResponseWriter, r *http.Request) {
  	if buh.Upload == nil {
  		buh.Errors = append(buh.Errors, v2.ErrorCodeBlobUploadUnknown)
  		return
  	}
  
  	w.Header().Set("Docker-Upload-UUID", buh.UUID)
  	if err := buh.Upload.Cancel(buh); err != nil {
  		dcontext.GetLogger(buh).Errorf("error encountered canceling upload: %v", err)
  		buh.Errors = append(buh.Errors, errcode.ErrorCodeUnknown.WithDetail(err))
  	}
  
  	w.WriteHeader(http.StatusNoContent)
  }
docs: // CancelBlobUpload cancels an in-progress upload of a blob.