better API for changing epoch calculation function

uuid.go

@@ -79,12 +79,14 @@ func unixTimeFunc() uint64 {
 	return epochStart + uint64(time.Now().UnixNano() / 100)
 }
 
+// Returns current epoch calculation function.
+func GetEpochFunc() (func() uint64) {
+	return epochFunc
+}
+
 // Sets epoch calculation function.
-// Returns old function.
-func SetEpochFunc(newEpochFunc func() uint64) (func() uint64) {
-	oldEpochFunc := epochFunc
+func SetEpochFunc(newEpochFunc func() uint64) {
 	epochFunc = newEpochFunc
-	return oldEpochFunc
 }
 
 // UUID representation compliant with specification

uuid_test.go

@@ -95,13 +95,16 @@ func TestNewV1(t *testing.T) {
 		t.Errorf("UUIDv1 generated two equal UUIDs: %s and %s", u1, u2)
 	}
 
-	oldFunc := uuid.SetEpochFunc(func() uint64 { return 0})
+	oldFunc := uuid.GetEpochFunc()
+
+	uuid.SetEpochFunc(func() uint64 { return 0})
 	u3, _ := uuid.NewV1()
 	u4, _ := uuid.NewV1()
 
 	if uuid.Equal(u3, u4) {
 		t.Errorf("UUIDv1 generated two equal UUIDs: %s and %s", u3, u4)
 	}
+
 	uuid.SetEpochFunc(oldFunc)
 }