My gas dryer starts fine than the flame goes out

Try YouTube dryer repair instructions. Here is a link to get started:
https://www.youtube.com/results?search_query=WGD9200SQ0+gas+dryer+lights+up+in+beginning+for+about+2+minutes+then+flame+goes+out

You will need to replace the gas coils. Here is a link to the parts.
Here is a video to walk you thru the process.

you have bad gas coils located on top of the gas valve

The pilot light lights? Then goe's back out? There is two stiff wires right in front of the flame. One of them is an ignightor, and the other one a thermocoupler. Or may just be one. That is the ignightor and thermocoupler. The thermocoupler is what detects that the pilot light lit. Its a saftey feature. It makes sure that there is fire before it turns on the main gas. So it wont blow up. It gets a film built up on it from the gas. Take some real fine sandpaper, or steel wool and clean it real good.
Then try again. It should work. If not then it needs to be replaced

you are obviously having igniter problems Call an authorized gas appliance serviceman before you have more very serious problems

The gas valve coils are closing the valve or the flame sensor is defective. The coils are the most common problem.
There are 2 on top of the gas valve. Turn off the gas and power. Remove the front panel by opening the top lid and then remove the screws from inside the front panel in the top right and left corners.

sounds like bad gas coils they are the two black coils that are on the top of gas valve

The 'radiant sensor/ needs to be replaced. This sensor tells the system that the flame is lit and everything is good. Go to repairclinic.com

http://www.repairclinic.com/SSPartDetail.aspx?s=t-mdg5500aww-%3d%3di2681&PartID=2681

If you need further help, I’m available over the phone at https://www.6ya.com/expert/craig_3fa289bf857b1a3c

If this unit has a pilot flame, the breather around the pilot flame has become dusty. The best way to clean it out is with high pressure air.
It wouldn't hurt to clean with high pressure air anyhow.
See how that goes.

should have electronic igniter that light gas after turned on.