build

#!/usr/bin/env bash
set -eo pipefail

echo "---> Go Buildpack"

# 1. GET ARGS
layers_dir=$1
plan_path=$3

# 2. DOWNLOAD go
go_layer_dir="${layers_dir}/go"
mkdir -p "${go_layer_dir}"
arch=$(dpkg --print-architecture)  # amd64 arm64
# determine go version provided during detection
go_version=$(< "${plan_path}" yj -t | jq -r '.entries[] | select(.name == "go") | .version')
remote_go_version='not found'
if [[ -f "${go_layer_dir}.toml" ]]; then
    remote_go_version=$(< "${go_layer_dir}.toml" yj -t | jq -r .metadata 2>/dev/null || echo 'not found')
fi
if [[ "${go_version}" == "${remote_go_version}" ]] ; then
  echo "---> Reusing go"
else
  echo "---> Downloading and extracting go ${go_version}"
  go_url=https://golang.org/dl/go${go_version}.linux-${arch}.tar.gz
  wget -q -O - "${go_url}" | tar -xzf - -C "${go_layer_dir}"
  cat > "${go_layer_dir}.toml" <<EOL
cache = true
build = true
launch = true
metadata = "${go_version}"
EOL
fi

go_cache_layer_dir="${layers_dir}/go_cache"
# 3. MAKE go AVAILABLE TO THIS SCRIPT
export PATH="${go_layer_dir}/go/bin:${PATH}"
export GOPATH="${go_cache_layer_dir}"

# Compares previous go.mod checksum to the current go.mod
local_mod_checksum=$(sha256sum go.mod | cut -d ' ' -f 1 || echo 'not found')
remote_mod_checksum='not found'
if [[ -f "${go_cache_layer_dir}.toml" ]]; then
    remote_mod_checksum=$(< "${go_cache_layer_dir}.toml" yj -t | jq -r .metadata 2>/dev/null || echo 'not found')
fi
mkdir -p "${go_cache_layer_dir}"

if [[ -f go.mod && "${local_mod_checksum}" == "${remote_mod_checksum}" ]] ; then
  echo "---> Reusing go.mod"
else
  echo "---> Installing go.mod with go mod vendor"
  rm "${go_cache_layer_dir}/pkg" -rf
  go mod download
  cat > "${go_cache_layer_dir}.toml" <<EOL
cache = true
build = true
launch = true
metadata = "${local_mod_checksum}"
EOL
fi

go mod vendor
go build -o main -v .
generate-launch.sh "${layers_dir}"