Upgrade go to 1.18

Linter issue

Fix: spread data parsing and re-subscribing to private channels

Add some constants

Add USDT instruments to web socket

Workflow. REST API actualize

Feature: cancel all orders after

Optional fields for AddOrderRequest

Add UnsubscribeCandles and UnsubscribeBook (aopoltorzhicky#31)

* Add UnsubscribeCandles and UnsubscribeBook

go mod tidy