Returns the values associated with the specified fields in the hash stored at
key.
For every field that does not exist in the hash, a nil value is returned.
Because a non-existing keys are treated as empty hashes, running HMGET against
a non-existing key will return a list of nil values.
@return
@array-reply: list of values associated with the given fields, in the same order as they are requested.
HSET myhash field1 "Hello"
HSET myhash field2 "World"
HMGET myhash field1 field2 nofield