adding IsNil method to uuid (#95)

* adding IsZero method to uuid

* rename isZero to IsNil

uuid.go

@@ -151,6 +151,11 @@ var (
 	NamespaceX500 = Must(FromString("6ba7b814-9dad-11d1-80b4-00c04fd430c8"))
 )
 
+// IsNil returns if the UUID is equal to the nil UUID
+func (u UUID) IsNil() bool {
+	return u == Nil
+}
+
 // Version returns the algorithm version used to generate the UUID.
 func (u UUID) Version() byte {
 	return u[6] >> 4

uuid_test.go

@@ -29,6 +29,7 @@ import (
 )
 
 func TestUUID(t *testing.T) {
+	t.Run("IsNil", testUUIDIsNil)
 	t.Run("Bytes", testUUIDBytes)
 	t.Run("String", testUUIDString)
 	t.Run("Version", testUUIDVersion)
@@ -38,6 +39,15 @@ func TestUUID(t *testing.T) {
 	t.Run("Format", testUUIDFormat)
 }
 
+func testUUIDIsNil(t *testing.T) {
+	u := UUID{}
+	got := u.IsNil()
+	want := true
+	if got != want {
+		t.Errorf("%v.IsNil() = %t, want %t", u, got, want)
+	}
+}
+
 func testUUIDBytes(t *testing.T) {
 	got := codecTestUUID.Bytes()
 	want := codecTestData