Sets field in the hash stored at key to value, only if field does not
yet exist.
If key does not exist, a new key holding a hash is created.
If field already exists, this operation has no effect.
@return
@integer-reply, specifically:
1iffieldis a new field in the hash andvaluewas set.0iffieldalready exists in the hash and no operation was performed.
@examples
HSETNX myhash field "Hello"
HSETNX myhash field "World"
HGET myhash field