diff --git a/FastGithub.DomainResolve/DnsClient.cs b/FastGithub.DomainResolve/DnsClient.cs
index dd47af3..f89edc9 100644
--- a/FastGithub.DomainResolve/DnsClient.cs
+++ b/FastGithub.DomainResolve/DnsClient.cs
@@ -46,11 +46,10 @@ namespace FastGithub.DomainResolve
         {
             var key = $"{dns}:{domain}";
             var semaphore = this.semaphoreSlims.GetOrAdd(key, _ => new SemaphoreSlim(1, 1));
+            await semaphore.WaitAsync(CancellationToken.None);
 
             try
             {
-                await semaphore.WaitAsync(CancellationToken.None);
-
                 if (this.dnsCache.TryGetValue<IPAddress[]>(key, out var value) == false)
                 {
                     value = await this.LookupCoreAsync(dns, domain, cancellationToken);
diff --git a/FastGithub.DomainResolve/DomainResolver.cs b/FastGithub.DomainResolve/DomainResolver.cs
index b894e52..7c8003a 100644
--- a/FastGithub.DomainResolve/DomainResolver.cs
+++ b/FastGithub.DomainResolve/DomainResolver.cs
@@ -78,6 +78,7 @@ namespace FastGithub.DomainResolve
             if (cryptDns != null)
             {
                 yield return cryptDns;
+                yield return cryptDns;
             }
 
             foreach (var fallbackDns in this.fastGithubConfig.FallbackDns)