Detect empty expiry with IsZero()

cache.go

@@ -101,7 +101,7 @@ func (c *cache) get(qname string) RRs {
 		rrs := make(RRs, len(e))
 		now := time.Now()
 		for rr, _ := range e {
-			if rr.Expiry != emptyTime && now.After(rr.Expiry) {
+			if !rr.Expiry.IsZero() && now.After(rr.Expiry) {
 				delete(e, rr)
 			} else {
 				rrs[i] = rr

resolver_test.go

@@ -193,7 +193,7 @@ func TestTTL(t *testing.T) {
 	st.Expect(t, err, nil)
 	st.Expect(t, len(rrs) >= 4, true)
 	rr := rrs[0]
-	st.Expect(t, rr.Expiry != emptyTime, true)
+	st.Expect(t, !rr.Expiry.IsZero(), true)
 }
 
 var testResolver *Resolver

rr.go

@@ -24,9 +24,6 @@ type RRs []RR
 // It is used to save allocations at runtime.
 var emptyRRs = RRs{}
 
-// emptyTime is used to detect an empty expiry time.
-var emptyTime = time.Time{}
-
 // ICANN specifies that DNS servers should return the special value 127.0.53.53
 // for A record queries of TLDs that have recently entered the root zone,
 // that have a high likelyhood of colliding with private DNS names.
@@ -37,7 +34,7 @@ const NameCollision = "127.0.53.53"
 
 // String returns a string representation of an RR in zone-file format.
 func (rr *RR) String() string {
-	if rr.Expiry == emptyTime {
+	if rr.Expiry.IsZero() {
 		return rr.Name + "\t      3600\tIN\t" + rr.Type + "\t" + rr.Value
 	} else {
 		ttl := ttlString(rr.TTL)