An example golang-based Buildkite Agent 2.x Docker image with custom pre-checkout hook for Go projects

Dockerfile

FROM golang:1.8

RUN apt-get update && \
  apt-get install -y apt-transport-https \
  && echo 'deb https://apt.buildkite.com/buildkite-agent stable main' > /etc/apt/sources.list.d/buildkite-agent.list \
  && apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys 32A37959C2FA5C3C99EFBC32A79206696452D198 \
  && apt-get update \
  && apt-get install -y buildkite-agent

COPY pre-checkout.sh /etc/buildkite-agent/hooks/pre-checkout

CMD ["buildkite-agent", "start"]

pre-checkout.sh

#!/bin/bash

set -eu

if [[ ! -z "${BUILDKTE_GOLANG_IMPORT_PATH:-}" ]]; then
  echo "--- :golang: Setting up Golang build environment"
  export GOPATH="$BUILDKITE_BUILD_CHECKOUT_PATH"
  export BUILDKITE_BUILD_CHECKOUT_PATH="$BUILDKITE_BUILD_CHECKOUT_PATH/src/$BUILDKTE_GOLANG_IMPORT_PATH"
fi

Usage.md

$ chmod +x pre-checkout.sh
...
$ docker build -t go-bk-agent .
...
$ docker run -e BUILDKITE_AGENT_TOKEN=xxx buildkite-agent start
...

If you're using Buildkite Agent 3+ you should just use the Golang Buildkite Agent Plugin