AC Milan's starting goalkeeper currently is Ciprian Tatarusanu, at least until the return of Mike Maignan who is still in recovery phase.
Tatarusanu's deal expires at the end of the season and it may be safe to say that he will not remain at the club once this campaign is over. His performances have also hurt the Rossoneri team a lot in terms of results and that is why Paolo Maldini and Frederic Massara want a reliable backup for Maignan next season.
According to what is reported by Calciomercato.com, AC Milan have indeed com to terms with Marco Sportiello -whose deal with Atalanta expires this June 30 - and the agreement has been in place for quite some time now already. The signing of the contracts, however, is not done just yet. As per the source, it is "expected in the next few days."