add dns handler

pkg/resolver/resolver.go

@@ -0,0 +1,11 @@
+package resolver
+
+import (
+	"context"
+	"net"
+)
+
+type Resolver interface {
+	// Resolve returns a slice of the host's IPv4 and IPv6 addresses.
+	Resolve(ctx context.Context, host string) ([]net.IP, error)
+}