Returns all fields and values of the hash stored at key
.
In the returned value, every field name is followed by its value, so the length
of the reply is twice the size of the hash.
@return
@array-reply: list of fields and their values stored in the hash, or an
empty list when key
does not exist.
@examples
HSET myhash field1 "Hello"
HSET myhash field2 "World"
HGETALL myhash