增加dns查询超时时长

FastGithub.Scanner/LookupProviders/PublicDnsProvider.cs

@@ -80,7 +80,10 @@ namespace FastGithub.Scanner.LookupProviders
             {
                 try
                 {
-                    var addresses = await client.Lookup(domain, cancellationToken: cancellationToken);
+                    using var timeoutTokenSource = new CancellationTokenSource(this.options.CurrentValue.Timeout);
+                    using var linkedTokenSource = CancellationTokenSource.CreateLinkedTokenSource(timeoutTokenSource.Token, cancellationToken);
+
+                    var addresses = await client.Lookup(domain, cancellationToken: linkedTokenSource.Token);
                     foreach (var address in addresses)
                     {
                         if (address.AddressFamily == AddressFamily.InterNetwork)

FastGithub.Scanner/LookupProviders/PublicDnsProviderOptions.cs

@@ -13,6 +13,11 @@ namespace FastGithub.Scanner.LookupProviders
         /// </summary>
         public bool Enable { get; set; } = true;
 
+        /// <summary>
+        /// dns查询超时时长
+        /// </summary>
+        public TimeSpan Timeout { get; set; } = TimeSpan.FromMilliseconds(100d);
+
         /// <summary>
         /// dns列表
         /// </summary>

FastGithub/appsettings.json

@@ -24,6 +24,7 @@
       },
       "PublicDnsProvider": {
         "Enable": true, // 是否需要从dns服务器查找ip
+        "Timeout": "00:00:00.100", // dns查询超时时长
         "Dnss": [ // dns服务器列表
           "1.2.4.8",
           "8.8.8.8",