NewStoreMemory returns a new standard memory store for captchas with the given collection threshold and expiration time (duration).

NewStoreSyncMap create a new sync map store.

Expiration time of captchas used by default store.

GCLimitNumber The number of captchas created that triggers garbage collection used by default store.

Store An object implementing Store interface can be registered with SetCustomStore function to handle storage and retrieval of captcha ids and solutions for them, replacing the default memory store.