race

server.go

@@ -10,17 +10,19 @@ import (
 	"net"
 	"net/http"
 	"strings"
+	"sync"
 	"time"
 
 	"golang.org/x/time/rate"
 )
 
 type Server struct {
-	Transport http.RoundTripper
-	resolver  *net.Resolver
-	limiter   *rate.Limiter
-	Timeout   time.Duration
-	dnsCache  map[string]dns
+	Transport    http.RoundTripper
+	resolver     *net.Resolver
+	limiter      *rate.Limiter
+	Timeout      time.Duration
+	dnsCacheLock sync.Mutex
+	dnsCache     map[string]dns
 }
 
 type dns struct {
@@ -154,6 +156,8 @@ func (s *Server) dig(ctx context.Context, host string) (string, error) {
 	search := host
 	search = strings.TrimPrefix(search, "https://")
 	search = strings.TrimPrefix(search, "http://")
+	s.dnsCacheLock.Lock()
+	defer s.dnsCacheLock.Unlock()
 	if v, ok := s.dnsCache[host]; ok && v.ok() {
 		return v.result, v.err
 	}