Last night http://codereview.appspot.com/4527098 was committed which allows Go to build under Clang 2.9.

% CC=/opt/local/bin/clang ./make.bash

Big props to Jeff Hodges for making this happen.

note: OS X users should be aware that Apple ship an older version of Clang if you have the XCode 4 tools installed. You should set CC to the absolute path to avoid confusion.