It is now possible, thanks to this adapter.  You can use a lavalier mic, a Rode Smart Lav or shotgun mic, and many other external microphones. 

But for this to work, you must use this adapter along with the original, Google OEM USB-C headphone adapter that came with the phone. 

See the last photo in this listing which shows the proper set-up to get an external microphone working on a Pixel phone.

Contacts are gold-plated for optimal connection and corrosion resistance.  The adapter is approximately 5.75" long, overall.

This listing includes only the black-colored adapter you see in the first three photos that accompany this listing.  It does not include the white-colored OEM Google USB-C headphone adapter, nor the microphone, nor the Pixel phone (of course).

This will ship the same day as you order.  See my feedback to confirm my excellent service, high-quality products, and quick shipping.

Any questions, please ask.