fixed struct alignment && refactor linter (#369)

## Pull Request template
Please, go through these steps before clicking submit on this PR.

1. Give a descriptive title to your PR.
2. Provide a description of your changes.
3. Make sure you have some relevant tests.
4. Put `closes #XXXX` in your comment to auto-close the issue that your PR fixes (if applicable).

**PLEASE REMOVE THIS TEMPLATE BEFORE SUBMITTING**

Reviewed-on: #369
Co-authored-by: Evstigneev Denis <danteevstigneev@yandex.ru>
Co-committed-by: Evstigneev Denis <danteevstigneev@yandex.ru>

util/dns/cache.go

@@ -43,7 +43,7 @@ func NewNetDialer(parent DialFunc, opts ...Option) DialFunc {
 	if cache.opts.MaxCacheEntries == 0 {
 		cache.opts.MaxCacheEntries = DefaultMaxCacheEntries
 	}
-	return func(ctx context.Context, network, address string) (net.Conn, error) {
+	return func(_ context.Context, network, address string) (net.Conn, error) {
 		conn := &dnsConn{}
 		conn.roundTrip = cachingRoundTrip(&cache, network, address)
 		return conn, nil
@@ -132,12 +132,12 @@ func PreferIPV6(b bool) Option {
 }
 
 type cache struct {
-	sync.RWMutex
-
-	dial    DialFunc
 	entries map[string]cacheEntry
+	dial    DialFunc
 
 	opts Options
+
+	sync.RWMutex
 }
 
 type cacheEntry struct {
@@ -306,7 +306,7 @@ func getNameLen(msg string) int {
 	for i < len(msg) {
 		if msg[i] == 0 {
 			// end of name
-			i += 1
+			i++
 			break
 		}
 		if msg[i] >= 0xc0 {
@@ -336,8 +336,7 @@ func cachingRoundTrip(cache *cache, network, address string) roundTripper {
 		cache.opts.Meter.Counter(semconv.CacheRequestInflight, "type", "dns").Inc()
 		defer cache.opts.Meter.Counter(semconv.CacheRequestInflight, "type", "dns").Dec()
 		// check cache
-		if res := cache.get(req); res != "" {
-			cache.opts.Meter.Counter(semconv.CacheRequestTotal, "type", "dns", "method", "get", "status", "hit").Inc()
+		if res = cache.get(req); res != "" {
 			return res, nil
 		}
 		cache.opts.Meter.Counter(semconv.CacheRequestTotal, "type", "dns", "method", "get", "status", "miss").Inc()

util/dns/cache_test.go

@@ -8,15 +8,13 @@ import (
 func TestCache(t *testing.T) {
 	net.DefaultResolver = NewNetResolver(PreferIPV4(true))
 
-	addrs, err := net.LookupHost("unistack.org")
+	_, err := net.LookupHost("unistack.org")
 	if err != nil {
 		t.Fatal(err)
 	}
 
-	addrs, err = net.LookupHost("unistack.org")
+	_, err = net.LookupHost("unistack.org")
 	if err != nil {
 		t.Fatal(err)
 	}
-
-	_ = addrs
 }

util/dns/conn.go

@@ -11,12 +11,15 @@ import (
 )
 
 type dnsConn struct {
-	deadline  time.Time
 	ctx       context.Context
 	cancel    context.CancelFunc
 	roundTrip roundTripper
-	ibuf      bytes.Buffer
-	obuf      bytes.Buffer
+
+	deadline time.Time
+
+	ibuf bytes.Buffer
+	obuf bytes.Buffer
+
 	sync.Mutex
 }
 
@@ -81,7 +84,7 @@ func (c *dnsConn) SetReadDeadline(t time.Time) error {
 	return nil
 }
 
-func (c *dnsConn) SetWriteDeadline(t time.Time) error {
+func (c *dnsConn) SetWriteDeadline(_ time.Time) error {
 	// writes do not timeout
 	return nil
 }
@@ -159,23 +162,22 @@ func readMessage(c net.Conn) (string, error) {
 			return "", err
 		}
 		return string(b[:n]), nil
-	} else {
-		var sz [2]byte
-		_, err := io.ReadFull(c, sz[:])
-		if err != nil {
-			return "", err
-		}
-
-		size := int64(sz[0])<<8 | int64(sz[1])
-
-		var str strings.Builder
-		_, err = io.CopyN(&str, c, size)
-		if err == io.EOF {
-			return "", io.ErrUnexpectedEOF
-		}
-		if err != nil {
-			return "", err
-		}
-		return str.String(), nil
 	}
+	var sz [2]byte
+	_, err := io.ReadFull(c, sz[:])
+	if err != nil {
+		return "", err
+	}
+
+	size := int64(sz[0])<<8 | int64(sz[1])
+
+	var str strings.Builder
+	_, err = io.CopyN(&str, c, size)
+	if err == io.EOF {
+		return "", io.ErrUnexpectedEOF
+	}
+	if err != nil {
+		return "", err
+	}
+	return str.String(), nil
 }