He was the youngest of a large family living in Sainte-Famille, on the eastern side of Île d'Orléans east of the city of Quebec.

Gosselin participated in the American attack on Quebec City on December 31, 1775, probably serving in James Livingston's 1st Canadian Regiment.

On November 28, 1778, Gosselin, following a spy mission to Quebec, sent a report on the state of the British force in Canada to Washington.

On October 4, 1781, he was severely wounded in the leg during the Siege of Yorktown, due to wood splinters sent flying by a cannonball.

[8] Gosselin was featured in the CBC Television series Canada: A People's History as one of a number of French-Canadians who not only sympathized with the American cause, but was willing to fight for them against the British.