Golang Installation script

install_golang.sh

#!/usr/bin/env bash
# Golang Installation Script (c) Brian 'redbeard' Harrington, 2019
#
# I'm very about how Golang is installed on my system.  I normally run through
# this entire process by hand, but realized that it's easier to just have this
# thing to do the needful.  Funny enough, 1.13.6 was published in the middle of
# me working on it, so it is already useful.
#
# In the future, I may add a "VERSION" env variable to allow for arbitrary
# versions rather than the latest stable.
#
# NOTE: This is not sorting the JSON returned by the Go website, so it's up to
# the server side.  This just takes the first value returned.
#
# requires jq and curl
#

PREFIX=${PREFIX:-/usr/local/golang}

set -eu -o pipefail

function finish {
  rm -rf "$scratch" 
}
trap finish EXIT

scratch=$(mktemp -d /tmp/.golang-setup-XXXX)

info="$(curl -sL "https://golang.org/dl/?mode=json" | jq -r '[.[].files[] | select(.filename | test("go.+linux-amd64.tar.gz"; "sx"))][0]')"

# extract invidivual values
filename=$(echo ${info} | jq -r .filename )
version=$(echo ${info} | jq -r .version )
version=${version#go*}
sha256=$(echo ${info} | jq -r .sha256 )

function dl_go() {

  curl -Lo ${scratch}/${filename} https://golang.org/dl/${filename}

  HASH="$(sha256sum -b ${scratch}/${filename} | cut -c-64)"

  if [ "${HASH}" != "${sha256}" ]; then
    echo "SHA 256 Hash failed, aborting install"
    exit 1
  fi

  echo "SHA 256 Hash verified , installing golang"
}

if [ ! -d ${PREFIX}/${version} ]; then
  dl_go
  mkdir -v -p ${PREFIX}/$version
  tar xvf ${scratch}/${filename} -C ${PREFIX}/${version}
  ln -sfr -T ${PREFIX}/${version} ${PREFIX}/latest
else
  echo "Latest version already installed at ${PREFIX}/${version}"
fi