Pull request: replace agherr with golibs' errors

Merge in DNS/adguard-home from golibs-errors to master

Squashed commit of the following:

commit 5aba278a31c5a213bd9e08273ce7277c57713b22
Author: Ainar Garipov <A.Garipov@AdGuard.COM>
Date:   Mon May 24 17:05:18 2021 +0300

    all: imp code

commit f447eb875b81779fa9e391d98c31c1eeba7ef323
Author: Ainar Garipov <A.Garipov@AdGuard.COM>
Date:   Mon May 24 15:33:45 2021 +0300

    replace agherr with golibs' errors

internal/aghio/limitedreadcloser.go

@@ -1,59 +0,0 @@
-// Package aghio contains extensions for io package's types and methods
-package aghio
-
-import (
-	"fmt"
-	"io"
-)
-
-// LimitReachedError records the limit and the operation that caused it.
-type LimitReachedError struct {
-	Limit int64
-}
-
-// Error implements error interface for LimitReachedError.
-// TODO(a.garipov): Think about error string format.
-func (lre *LimitReachedError) Error() string {
-	return fmt.Sprintf("attempted to read more than %d bytes", lre.Limit)
-}
-
-// limitedReadCloser is a wrapper for io.ReadCloser with limited reader and
-// dealing with agherr package.
-type limitedReadCloser struct {
-	limit int64
-	n     int64
-	rc    io.ReadCloser
-}
-
-// Read implements Reader interface.
-func (lrc *limitedReadCloser) Read(p []byte) (n int, err error) {
-	if lrc.n == 0 {
-		return 0, &LimitReachedError{
-			Limit: lrc.limit,
-		}
-	}
-	if int64(len(p)) > lrc.n {
-		p = p[0:lrc.n]
-	}
-	n, err = lrc.rc.Read(p)
-	lrc.n -= int64(n)
-	return n, err
-}
-
-// Close implements Closer interface.
-func (lrc *limitedReadCloser) Close() error {
-	return lrc.rc.Close()
-}
-
-// LimitReadCloser wraps ReadCloser to make it's Reader stop with
-// ErrLimitReached after n bytes read.
-func LimitReadCloser(rc io.ReadCloser, n int64) (limited io.ReadCloser, err error) {
-	if n < 0 {
-		return nil, fmt.Errorf("aghio: invalid n in LimitReadCloser: %d", n)
-	}
-	return &limitedReadCloser{
-		limit: n,
-		n:     n,
-		rc:    rc,
-	}, nil
-}

internal/aghio/limitedreader.go

@@ -0,0 +1,59 @@
+// Package aghio contains extensions for io package's types and methods
+package aghio
+
+import (
+	"fmt"
+	"io"
+)
+
+// LimitReachedError records the limit and the operation that caused it.
+type LimitReachedError struct {
+	Limit int64
+}
+
+// Error implements error interface for LimitReachedError.
+//
+// TODO(a.garipov): Think about error string format.
+func (lre *LimitReachedError) Error() string {
+	return fmt.Sprintf("attempted to read more than %d bytes", lre.Limit)
+}
+
+// limitedReader is a wrapper for io.Reader with limited reader and dealing with
+// errors package.
+type limitedReader struct {
+	r     io.Reader
+	limit int64
+	n     int64
+}
+
+// Read implements Reader interface.
+func (lr *limitedReader) Read(p []byte) (n int, err error) {
+	if lr.n == 0 {
+		return 0, &LimitReachedError{
+			Limit: lr.limit,
+		}
+	}
+
+	if int64(len(p)) > lr.n {
+		p = p[0:lr.n]
+	}
+
+	n, err = lr.r.Read(p)
+	lr.n -= int64(n)
+
+	return n, err
+}
+
+// LimitReader wraps Reader to make it's Reader stop with ErrLimitReached after
+// n bytes read.
+func LimitReader(r io.Reader, n int64) (limited io.Reader, err error) {
+	if n < 0 {
+		return nil, fmt.Errorf("aghio: invalid n in LimitReader: %d", n)
+	}
+
+	return &limitedReader{
+		r:     r,
+		limit: n,
+		n:     n,
+	}, nil
+}

internal/aghio/limitedreader_test.go

@@ -10,7 +10,7 @@ import (
 	"github.com/stretchr/testify/require"
 )
 
-func TestLimitReadCloser(t *testing.T) {
+func TestLimitReader(t *testing.T) {
 	testCases := []struct {
 		want error
 		name string
@@ -24,20 +24,20 @@ func TestLimitReadCloser(t *testing.T) {
 		name: "zero",
 		n:    0,
 	}, {
-		want: fmt.Errorf("aghio: invalid n in LimitReadCloser: -1"),
+		want: fmt.Errorf("aghio: invalid n in LimitReader: -1"),
 		name: "negative",
 		n:    -1,
 	}}
 
 	for _, tc := range testCases {
 		t.Run(tc.name, func(t *testing.T) {
-			_, err := LimitReadCloser(nil, tc.n)
+			_, err := LimitReader(nil, tc.n)
 			assert.Equal(t, tc.want, err)
 		})
 	}
 }
 
-func TestLimitedReadCloser_Read(t *testing.T) {
+func TestLimitedReader_Read(t *testing.T) {
 	testCases := []struct {
 		err   error
 		name  string
@@ -77,7 +77,7 @@ func TestLimitedReadCloser_Read(t *testing.T) {
 			readCloser := io.NopCloser(strings.NewReader(tc.rStr))
 			buf := make([]byte, tc.limit+1)
 
-			lreader, err := LimitReadCloser(readCloser, tc.limit)
+			lreader, err := LimitReader(readCloser, tc.limit)
 			require.NoError(t, err)
 
 			n, err := lreader.Read(buf)
@@ -87,7 +87,7 @@ func TestLimitedReadCloser_Read(t *testing.T) {
 	}
 }
 
-func TestLimitedReadCloser_LimitReachedError(t *testing.T) {
+func TestLimitedReader_LimitReachedError(t *testing.T) {
 	testCases := []struct {
 		err  error
 		name string