HI, I'm french my english is not very good. But, i want pass my game Don't Starve on steam. I need you. thanks you.
Sorry for the late response, but follow this link: http://support.kleientertainment.com/customer/en/portal/articles/1803621-i-bought-don-t-starve-from-gog-do-i-get-don-t-starve-together-on-steam-
GOG will not provide you with a Steam key. The game company (Klei) will provide you with a Steam key if you bought Don't Starve before June 3rd, 2015, by following the link above and sending them an e-mail.
If you bought Don't Starve more recently (after June 2015), you may not be eligible for a Steam key. But, you can try contacting them anyway to see what they say.