Warning: Unable To Verify The First Certificate

Hello. I was created a question on stackoverflow. Please look at this link to get more details so I don’t repeat myself.

Brief details: I was testing my API and everything works great but I found some warning that worrying me.

I’ve already visited some links relative to problems like this and tried to use some advices and solutions from them but nothing helps. This links attached to my question on stackoverflow so please take a look at this link. Any help wiil be appreciated.