Nexus 5x stuck in download mode after flashing
There was no specific question posted, so I asume you have your phone bricked (unusable) now, and you want to get it out of that state.
Here you find a few alternatives:


Two people reported here that unplugging the cable, then holding the power button down restarts the phone, and it likely brings it back to life. Similarly here... And there are plenty of similar posts around.
You commented that this does not work.
There are further instructions here.
From here: 
"If a battery pull doesn't fix the problem, turn your phone off, charge the battery sufficiently (while it's off) and then unplug from the charger. Hold Volume Down and Power to enter HBoot and enter recovery. Once you see the error symbol pull the battery out again and then reinsert the battery and start as normal. This (for some reason) works for a lot of people. If all else fails enter recovery and do a factory reset."