Pull request: scripts: improve go-lint

Merge in DNS/adguard-home from imp-lint-script to master

Squashed commit of the following:

commit 89a6e8343f9f0c7ea257899b5daac014bfb6b6df
Author: Ainar Garipov <A.Garipov@AdGuard.COM>
Date:   Thu Dec 10 13:36:38 2020 +0300

    script: make go-lint more in line with HACKING.md

commit dc4e1519d25877a074f667fec696578c80d7baf3
Author: Ainar Garipov <A.Garipov@AdGuard.COM>
Date:   Thu Dec 10 13:35:03 2020 +0300

    scripts: improve go-lint

HACKING.md

@@ -152,6 +152,8 @@ The rules are mostly sorted in the alphabetical order.
 
  *  Put spaces within `$( cmd )`, `$(( expr ))`, and `{ cmd; }`.
 
+ *  `snake_case`, not `camelCase`.
+
  *  Use `set -e -f -u` and also `set -x` in verbose mode.
 
  *  Use the `"$var"` form instead of the `$var` form, unless word splitting is