Modal "will can" [closed]

The non-standard double modal construction — although here you're talking about a periphastic future where can functions as the infinitive — is a feature of everyday speech in the North of England, Scotland, then through Northern Ireland to the American South. In reference to the latter usage, the Yale Grammatical Diversity Project prefers the term multiple modals, since including quasimodals, the number is occasionally not limited to two:

I reckon I might should better try to get me a little bit more sleep.

Not all possible combinations appear, and even those theoretically allowed by the grammar of this construction are neither in use in all four regions nor of equal frequency, even among individual speakers.

As this chart shows, will can is not used in the American South, so the author of your post must be from one of the other three regions in the UK.