Indentation in Go: tabs or spaces?

Question

Is there a standard Google Go coding conventions document somewhere that sets whether tabs or spaces are preferred for indentation in Go source code?

What is the official

Answer 1

EDIT 2: he original answer at the bottom is now incorrect. The correct section of the linked source file (current 30/12/2019) is:

Gofmt formats Go programs. It uses tabs for indentation and blanks for alignment. Alignment assumes that an editor is using a fixed-width font.

Thanks to TehSphinX for pointing this out!

ALL INFO BELOW THIS LINE IS NOW INCORRECT

EDIT: The original answer at the bottom is now incorrect. The correct section of the linked source file (current 25/07/2014) is:

Gofmt formats Go programs.
It uses tabs (width = 8) for indentation and blanks for alignment.

Original answer (deprecated):

Formatting control flags:
    -comments=true
        Print comments; if false, all comments are elided from the output.
    -tabs=true
        Indent with tabs; if false, spaces are used instead.
    -tabwidth=8
        Tab width in spaces.