Go isn't specifically a "systems programming language", it's a general purpose programming language.
You don't need any prior knowledge of C to get started, it's not very close to C at all (even syntactically).
You don't need specific systems concepts (Unix or otherwise) either. A fair understanding of how to get things done on the command line and how to use a text editor are pretty much all you need - and since you can do the Tour of Go entirely from your favorite browser, even that's not required.
Go would be fine as a first programming language (except maybe that Go being a relatively young language, you might find a bit less documentation and tutorials around than for others, and the tools/ecosystem might have a few more rough edges).
All you need is time to go through tutorials and introductory material on golang.org and elsewhere, patience, and curiosity.