diff --git a/pkg/captcha/captcha.go b/pkg/captcha/captcha.go
index 6e3b746..d1fcd20 100644
--- a/pkg/captcha/captcha.go
+++ b/pkg/captcha/captcha.go
@@ -38,9 +38,15 @@ type Captcha interface {
 // All derivatives that embed this struct only need to
 // implement Image() method.
 type BaseCaptcha struct {
-	Answer   Answer
-	Solved   bool
-	ExpireIn time.Time
+	answer   Answer
+	solved   bool
+	expireIn time.Time
+}
+
+func NewBaseCaptcha(expiry time.Duration) *BaseCaptcha {
+	return &BaseCaptcha{
+		expireIn: ExpiryDate(expiry),
+	}
 }
 
 func (c *BaseCaptcha) Image(style string) *image.Image {
@@ -48,23 +54,23 @@ func (c *BaseCaptcha) Image(style string) *image.Image {
 }
 
 func (c *BaseCaptcha) GetAnswer() Answer {
-	if c.Answer == "" {
-		c.Answer = NewIntAnswer()
+	if c.answer == "" {
+		c.answer = NewIntAnswer()
 	}
-	return c.Answer
+	return c.answer
 }
 
 func (c *BaseCaptcha) Solve(answer Answer) bool {
-	c.Solved = c.Answer == answer
-	return c.Solved
+	c.solved = c.answer == answer
+	return c.solved
 }
 
 func (c *BaseCaptcha) IsSolved() bool {
-	return c.Solved
+	return c.solved
 }
 
 func (c *BaseCaptcha) Expiry() time.Time {
-	return c.ExpireIn
+	return c.expireIn
 }
 
 func ExpiryDate(expiry time.Duration) time.Time {