Upgrade to Alpine 3.12

Dockerfile

@@ -1,4 +1,4 @@
-ARG ALPINE_VERSION=3.11
+ARG ALPINE_VERSION=3.12
 ARG GO_VERSION=1.14
 
 FROM golang:${GO_VERSION}-alpine${ALPINE_VERSION} AS builder

README.md

@@ -123,7 +123,7 @@
 Check the VPN IP address matches your expectations
 
 ```sh
-docker run --rm --network=container:gluetun alpine:3.11 wget -qO- https://ipinfo.io
+docker run --rm --network=container:gluetun alpine:3.12 wget -qO- https://ipinfo.io
 ```
 
 Want more testing? ▶ [see the Wiki](https://github.com/qdm12/private-internet-access-docker/wiki/Testing)