feat: Handle nameserver parsing on Windows

* system default nameserver in windows

* change

pkg/config/config_unix.go

@@ -0,0 +1,30 @@
+// +build !windows
+
+package config
+
+import (
+	"net"
+
+	"github.com/miekg/dns"
+)
+
+// DefaultResolvConfPath specifies path to default resolv config file on UNIX.
+const DefaultResolvConfPath = "/etc/resolv.conf"
+
+// GetDefaultServers get system default nameserver
+func GetDefaultServers() ([]string, int, []string, error) {
+	// if no nameserver is provided, take it from `resolv.conf`
+	cfg, err := dns.ClientConfigFromFile(DefaultResolvConfPath)
+	if err != nil {
+		return nil, 0, nil, err
+	}
+	servers := make([]string, 0)
+	for _, server := range cfg.Servers {
+		ip := net.ParseIP(server)
+		if isUnicastLinkLocal(ip) {
+			continue
+		}
+		servers = append(servers, server)
+	}
+	return servers, cfg.Ndots, cfg.Search, nil
+}