Mike saved Gao Guang a few times, which is hard to quantify, as he took several bullets for him.
From a common perspective, Gao Guang owed Mike several life-saving favors. However, considering their relationship as boss and subordinate, one couldn't really say Mike had saved Gao Guang's life since that was what he was being paid to do.
But regardless of the perspective, Mike's actions had fully proved he was indeed useful to Gao Guang, and extremely important at that.
If Gao Guang were an extreme egoist, he would find a way to tie Mike to his side for life, until Mike took a bullet for him and died.
If Gao Guang were a more refined egoist, he would find some excuses to bind Mike to his side, but the result would be the same: Mike would just be a lackey taking bullets for him until his death.
But Gao Guang was not an egoist. He had a typical Huaxia way of thinking, which valued balance and the middle ground, and deep down, there was likely a trait found only among Huaxian people.