function: fix race condition getting UASTs
function: fix race condition getting UASTs

When execution is parallel only one uastFunc is used. This makes its
hash to be used by more than one worker at the same time and producing
panics.

Another better way to solve this is having one uastFunc per worker
instead of only one.

Signed-off-by: Javi Fontan <bd6f2f0212e303b54f36d84bb19ae60fa8e400a6@gmail.com>

gitql/gitql,gitql/gitql