wireguard looses internet connection intermittently.

[Jason A. Donenfeld]

GCP uses an MTU of 1460 because Google's network does weird things.
That means the MTU for WireGuard should be 1380. On the GCP box, try
adding `MTU=1380` to your config and add this line to PostUp: `
; iptables -t mangle -A POSTROUTING -p tcp --tcp-flags SYN,RST SYN -j
TCPMSS --clamp-mss-to-pmtu`