Was booking return trip on YYZ-YUL and got this when I proceeded to book?

Select your Tango fare options

I prefer to enjoy the full benefits of my Tango fare.
I prefer to take advantage of the $ 10.00 Go Discount (per direction, per person) exclusively on aircanada.com and agree to the conditions below:

Limit of standard carry-on baggage allowance only. Excess Baggage fees will apply for any checked baggage.
Flight changes or cancellations are not permitted. You can make a same day change for a flat fee of $150 CAD.
GO Discount is only available on aircanada.com.
Since when has this been availabel?