Wigan Athletic chief hails Lang before 'catastrophic' turnaround
Lang gave Latics a 33rd-minute lead with a quite magnificent individual effort, carrying the ball forward before rifling into the top corner from fully 30 yards.
Lang was also inches away from toeing home a cross from Viv Solomon-Otabor, and Richardson acknowledged his young forward couldn't have done any more for his side.
"Callum's one of those lads who are doing so much for the cause," said the Latics boss.
"He looks fit, he looks strong, and his goals will hopefully help in our quest to get to where we want to be.
"I thought his performance levels absolutely epitomise where we want to be.
"We set a level, a bar, of application and effort, and we can't drop below that.
"And that's where my frustration comes from when we're not quite there, because I know what we're capable of.
"Again, that's one of the really disappointing things, because a goal of that much individual quality deserves to win any game.
"When you see a goal like that go in, having worked tirelessly hard to create it, you start to think this is going to be your day.
"But to see it slip away, once you've got a foothold in the game, it's catastrophic the way it happens.
"The response was good, the character was excellent, and the way we finished the game showed the fighting spirit we're going to need for the rest of the season. "
Richardson acknowledged the performance was miles better in every department than in midweek, when Latics were hammered 5-0 at home by Hull.
"The result's obviously disappointing, because obviously we're in an elite performance business, and results are everything," added Richardson.
"But certainly after what happened in midweek, what you're chasing is a reaction and a response, and I felt like we got that.
"If we'd have drawn the game we would have been slightly disappointed.
"To end up losing it, it's just another of those punches we're having to take, and we have to stay together as much as we can and look to the next game.
"I don't want to take anything away from Lincoln, they're an excellent footballing side and they've a lot of young lads playing with expression and creativity.
"But I felt we really imposed ourselves on the game, and even at the end we were coming on really strong, and had three or four really good chances that on another day you take and you get something."