Lock locks the `key` with writing lock.

LockFunc locks the `key` with writing lock and callback function `f`.

New creates and returns a new memory locker.

Remove removes mutex with given `key`.

RLock locks the `key` with reading lock.

RLockFunc locks the `key` with reading lock and callback function `f`.

RUnlock unlocks the reading lock of the `key`.

TryLock tries locking the `key` with writing lock, it returns true if success, or if there's a write/reading lock the `key`, it returns false.

TryLockFunc locks the `key` with writing lock and callback function `f`.

TryRLock tries locking the `key` with reading lock.

TryRLockFunc locks the `key` with reading lock and callback function `f`.

Unlock unlocks the writing lock of the `key`.

Locker is a memory based locker.