Read response payload.

async def read(self) -> bytes:
        """Read response payload."""
        if self._body is None:
            try:
                self._body = await self.content.read()
                for trace in self._traces:
                    await trace.send_response_chunk_received(self._body)
            except BaseException:
                self.close()
                raise
        elif self._released:
            raise ClientConnectionError('Connection closed')

        return self._body