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/home/authglinet.go

@@ -73,22 +73,27 @@ func glGetTokenDate(file string) uint32 {
 	f, err := os.Open(file)
 	if err != nil {
 		log.Error("os.Open: %s", err)
+
 		return 0
 	}
-	defer f.Close()
+	defer func() {
+		derr := f.Close()
+		if derr != nil {
+			log.Error("glinet: closing file: %s", err)
+		}
+	}()
 
-	fileReadCloser, err := aghio.LimitReadCloser(f, MaxFileSize)
+	fileReader, err := aghio.LimitReader(f, MaxFileSize)
 	if err != nil {
 		log.Error("creating limited reader: %s", err)
 
 		return 0
 	}
-	defer fileReadCloser.Close()
 
 	var dateToken uint32
 
 	// This use of ReadAll is now safe, because we limited reader.
-	bs, err := io.ReadAll(fileReadCloser)
+	bs, err := io.ReadAll(fileReader)
 	if err != nil {
 		log.Error("reading token: %s", err)