inbound.go
func (response *InboundCallResponse) SendSystemError(err error) error {
	if response.err != nil {
		return response.err
	}
	// Fail all future attempts to read fragments
	response.state = reqResWriterComplete
	response.systemError = true
	response.doneSending()
	response.call.releasePreviousFragment()

	span := CurrentSpan(response.mex.ctx)

	return response.conn.SendSystemError(response.mex.msgID, *span, err)
}
func (response *InboundCallResponse) SendSystemError(err error) error {
	if response.err != nil {
		return response.err
	}
	// Fail all future attempts to read fragments
	response.state = reqResWriterComplete
	response.systemError = true
	response.doneSending()
	response.call.releasePreviousFragment()

	span := CurrentSpan(response.mex.ctx)

	return response.conn.SendSystemError(response.mex.msgID, *span, err)
}
// SendSystemError returns a system error response to the peer.  The call is considered
// complete after this method is called, and no further data can be written.