Is this right K2S(aq) + MgCl2(aq) →MgS(s) + 2KCl(aq)

is the solid MgS the precipitate MgS ???

Writing a double replacement reaction predicts magnesium sulfide as the product but actually the potassium sulfide solution contains a fairly high concentration of hydroxide ions so the actual precipitate would be Magnesium Hydroxide!
S^=(aq) + H2O(l) <===> OH-(aq) + SH-(aq)
Mg^2+(aq) + 2 OH-(aq) -----> Mg(OH)2(s)