Do one fetch

def async_fetch(self, task, callback=None):
        '''Do one fetch'''
        url = task.get('url', 'data:,')
        if callback is None:
            callback = self.send_result

        type = 'None'
        start_time = time.time()
        try:
            if url.startswith('data:'):
                type = 'data'
                result = yield gen.maybe_future(self.data_fetch(url, task))
            elif task.get('fetch', {}).get('fetch_type') in ('js', 'phantomjs'):
                type = 'phantomjs'
                result = yield self.phantomjs_fetch(url, task)
            elif task.get('fetch', {}).get('fetch_type') in ('splash', ):
                type = 'splash'
                result = yield self.splash_fetch(url, task)
            elif task.get('fetch', {}).get('fetch_type') in ('puppeteer', ):
                type = 'puppeteer'
                result = yield self.puppeteer_fetch(url, task)
            else:
                type = 'http'
                result = yield self.http_fetch(url, task)
        except Exception as e:
            logger.exception(e)
            result = self.handle_error(type, url, task, start_time, e)

        callback(type, task, result)
        self.on_result(type, task, result)
        raise gen.Return(result)