Doku struck as City won 3-0 at Stamford Bridge.
The win takes City six points behind league-leaders Arsenal, who they face at the Etihad Stadium next Sunday, as well as having a game in hand over the Gunners.
“Obviously, three points here, in a tough game, we did very well. We needed those three points,” said Doku at the final whistle.
“So we’re just going to keep on going, keep on going. We know that we still have everything in our hands. We’re going to recover well and we look forward to the game on Sunday.
“Coming here is not easy, playing here against Chelsea in their stadium is not easy. We just had to keep on going.
“We adapted our pressing a bit and more runs in behind, that opens more spaces. The way we started the second half also put a lot of pressure on them. In those moments when you can score it helps a lot.”