Use the golang from buster-backports as out shapeshifter-dispatcher is pinned to

use go 1.13 so it can utilize go modules

Dockerfile

-FROM debian:buster AS build
+FROM debian:buster-backports AS build
 RUN apt-get -q update && env DEBIAN_FRONTEND=noninteractive apt-get install -y --no-install-recommends \
-    build-essential pkg-config golang-go git ca-certificates openvpn \
+        build-essential pkg-config git ca-certificates openvpn \
+&& DEBIAN_FRONTEND=noninteractive apt-get install -y --no-install-recommends -t buster-backports golang-go \
 && rm -rf /var/lib/apt/lists/*
 
 # don't need to do bash tricks to keep the layers small, as this is a multi-stage build