iOS: App在安装App时没有征求用户的许可，每次都没有确定kclauthorizationstatusnotsure——Objective-c & Swift

I am trying to fetch user location in my iOS app. I have included corelocation framework in my project first. Then on a button click I am invoking the core location api as below. When I am trying to install this in a device, the core location never asks the user permission. When I try to fetch the location on button click, I am getting kCLAuthorizationStatusNotDetermined as the authorisationStatus. Please help me in this. I have no clue what is happening.I am trying to fetch user location in my iOS ap