Based on [1] (where continue is handled) and [2] (the branch statement type), looks like the target is simply passed to the function. This is a recursive descent parser, so passing the target down the statement handling stack is trivial (and indeed, this is what happens for for[3]).

[1] https://github.com/golang/go/blob/master/src/cmd/compile/int... ("ctx" is a "targets" struct containing two entries, one for which statement 'break' targets and another for which statement 'continue' targets).

[2] https://github.com/golang/go/blob/master/src/cmd/compile/int...

[3] https://github.com/golang/go/blob/master/src/cmd/compile/int... (the targets{s, s} passed to innerBlock is then passed to blockBranches - s is the for statement node itself).

As a sidenote, it is interesting how easy Go reads even though i never wrote a single line of Go myself (though i do write a lot of C and Object Pascal and the code patterns look similar).