Open cs go and go to settings in the video tab.

First step:
Change your Aspect Ratio to NORMAL 4:3.

Second step:
Choose your desired resolution.
E.g 1400x1050 (highest), 1152x864 (middle), 640x480 (lowest).
Keep in mind, a higher resolution means less fps butt better quality , a lower resolution means more fps but a worst quality.

Third step:
Memorize your desired resolution, you will need it later.

Press Windows key to open Windows search bar, and search for Intel® Graphics Command Center. You can simply type Graphics Command Center on search bar and it will pop up. If you don't have it on your PC open Microsoft Store and search Intel® Graphics Command Center.

Once you opened Intel® Graphics Command Center

First step:
Go to display and look for resolution.

Second step:
Change your resolution to the one you chose in cs and change your current resolution to the one chosen in cs.
Press keep when the changing message will appear.

Third step:
Change your Scale to Stretched and press keep.

Fourth step:
Change back to your 1980:1080 resolution or whatever resolution you had before.

Now congrats! you got rid of black bars and your cs is now on 4:3 resolution without black bars

I will make a step-by-step tutorial on 1400:1050 resolution.
1. Open Cs and go to settings on video tab,
2. Change Aspect Ratio to NORMAL 4:3,
3. Change your Resolution to 1400:1050,
4. Quit Cs
5. Press windows key and search for Intel® Graphics Command Center,
6. Open Intel® Graphics Command Center and go to display,
7. Change your resolution to 1400:1050,
8. Change back to your previous resolution.

You are done now, the most important thing is to enjoy your "new" Cs.