Go buy beer sounds dreadful in English (but not American?). We would say "go and buy beer".
We don't really use the infinitive after the imperative of "go":
"I'm going to buy some beer"
BUT "Go and buy some beer" (BrE)
"Go buy some beer" (AmE)
I'm English and totally disagree. None of the options is technically wrong, but you would have been taught in school that "go to buy", "go to get" is the preferred form.
"Go and" isn't necessarily wrong, but is less formal and can sound a little lazy in some situations.
Just "go buy" sounds American and would sound very unnatural if said by a British native.
Exactly... In English, 'Go buy beer' would be extremely rude and anticipating a reply telling one to go and do some rather awkward things! 'Go and buy some beer' is very polite and much more normal.