Pull request: all: avoid fallthrough

Merge in DNS/adguard-home from rm-fallthrough to master

Squashed commit of the following:

commit 14308b6cd3580d2c51b6da9f40b8a37766046708
Author: Ainar Garipov <A.Garipov@AdGuard.COM>
Date:   Fri May 21 18:16:42 2021 +0300

    dhcpd: imp code

commit 2009219df7d35713d06848010ce57b387e407c0e
Author: Ainar Garipov <A.Garipov@AdGuard.COM>
Date:   Fri May 21 17:54:38 2021 +0300

    all: avoid fallthrough

scripts/make/go-lint.sh

@@ -106,6 +106,8 @@ underscores() {
 	}
 }
 
+# TODO(a.garipov): Add an analyser to look for `fallthrough`, `goto`, and `new`?
+
 
 
 # Helpers