。
Come hang out already.
Literal
Play-[purpose-に] come-[imperative-こい]-[sentence-final-よ].
こい is the rough imperative of 来る ('to come') — an irregular form. Paired with 遊びに and よ, it's a casual, slightly insistent invitation: 'c'mon, come over.' The level of brusqueness depends on tone — between close friends it's warm; to a stranger it's rude. Useful for seeing the bare imperative of 来る.