fix: race condition of Package fields

[ldez]

Related to #1306, it improves the situation (no race condition) but does not fix it fully.

$ ./revive-bench.sh
722
723
722
723
723
723
723
722
722
723

revive-bench.sh

#!/bin/bash -e

for a in {1..10}; do
    revive ./... | wc -l
done