optimize: dns delay & fallback

http.go

@@ -55,7 +55,10 @@ var cli = comandyClient(http.Client{
 			if len(addrs) == 0 {
 				addrs, err = resolver.LookupHost(ctx, host)
 				if err != nil {
-					return nil, err
+					addrs, err = net.DefaultResolver.LookupHost(ctx, host)
+					if err != nil {
+						return nil, err
+					}
 				}
 				lookupTable.Set(host, addrs)
 			}
@@ -80,7 +83,7 @@ var cli = comandyClient(http.Client{
 				}
 				_ = tlsConn.Close()
 			}
-			return tlsConn, nil
+			return tlsConn, err
 		},
 	},
 })

ipv6.go

@@ -1,13 +1,21 @@
 package main
 
 import (
+	"context"
 	"net/http"
+	"time"
 
 	"github.com/RomiChan/syncx"
 )
 
 var canUseIPv6 = syncx.Lazy[bool]{Init: func() bool {
-	resp, err := http.Get("http://v6.ipv6-test.com/json/widgetdata.php?callback=?")
+	ctx, cancel := context.WithTimeout(context.Background(), 4*time.Second)
+	defer cancel()
+	req, err := http.NewRequestWithContext(ctx, "GET", "http://v6.ipv6-test.com/json/widgetdata.php?callback=?", nil)
+	if err != nil {
+		return false
+	}
+	resp, err := http.DefaultClient.Do(req)
 	if err != nil {
 		return false
 	}