refactor(test): improve error check

Author: bashbunni

glow_test.go

@@ -2,7 +2,8 @@ package main
 
 import (
 	"bytes"
-	"strings"
+	"errors"
+	"net"
 	"testing"
 )
 
@@ -19,7 +20,8 @@ func TestGlowSources(t *testing.T) {
 		t.Run(v, func(t *testing.T) {
 			// Start by checking for network issues.
 			_, nerr := readmeURL(v)
-			if nerr != nil && strings.Contains(nerr.Error(), "no such host") {
+			var dnsErr *net.DNSError
+			if nerr != nil && errors.As(nerr, &dnsErr) {
 				t.Logf("Error during execution (args: %s):\n%v", v, nerr)
 				t.Skip("Test uses network. Are you connected to the Internet?")
 			}