change captcha default time

utils/captcha.go

 	theCap := cap{
 		Phone:   phone,
 		Captcha: capEngine.Random(6, phone),
-		Expire:  time.Now().Local().Add(1 * time.Minute),
+		Expire:  time.Now().Local().Add(3 * time.Minute),
 	}
 
 	c.capList[phone] = theCap