Pull request:* all: fix all staticcheck simplification and unused warnings

Merge in DNS/adguard-home from 2270-fix-s-u-warnings to master

Squashed commit of the following:

commit 03e0f78bd471057007c2d4042ee26eda2bbc9b29
Merge: 50dc3ef5c 7e16fda57
Author: Eugene Burkov <e.burkov@adguard.com>
Date:   Fri Nov 6 11:54:09 2020 +0300

    Merge branch 'master' into 2270-fix-s-u-warnings

commit 50dc3ef5c44a5fdc941794c26784b0c44d7b5aa0
Author: Eugene Burkov <e.burkov@adguard.com>
Date:   Thu Nov 5 19:48:54 2020 +0300

    * all: improve code quality

commit d6d804f759ce3e47154a389b427550e72c4b9090
Author: Eugene Burkov <e.burkov@adguard.com>
Date:   Thu Nov 5 18:03:35 2020 +0300

    * all: fix all staticcheck simplification and unused warnings

    Closes #2270.

internal/home/auth.go

@@ -27,14 +27,12 @@ type session struct {
 	expire   uint32 // expiration time (in seconds)
 }
 
-/*
-expire byte[4]
-name_len byte[2]
-name byte[]
-*/
 func (s *session) serialize() []byte {
-	var data []byte
-	data = make([]byte, 4+2+len(s.userName))
+	const (
+		expireLen = 4
+		nameLen   = 2
+	)
+	data := make([]byte, expireLen+nameLen+len(s.userName))
 	binary.BigEndian.PutUint32(data[0:4], s.expire)
 	binary.BigEndian.PutUint16(data[4:6], uint16(len(s.userName)))
 	copy(data[6:], []byte(s.userName))
@@ -474,7 +472,7 @@ func (a *Auth) UserAdd(u *User, password string) {
 }
 
 // UserFind - find a user
-func (a *Auth) UserFind(login string, password string) User {
+func (a *Auth) UserFind(login, password string) User {
 	a.lock.Lock()
 	defer a.lock.Unlock()
 	for _, u := range a.users {