update-alternatives-4-golang.sh

#!/bin/bash
#
# Use this script with sudo to install multiple golang
#  installations.

if [[ $(id -u) -ne 0 ]] ; then echo "This script should be run using
  sudo or as the root user" ; exit 1 ;
fi

# Ensure the user wants to rm the contents of /opt/golang!
read -p "This script will ERASE THE CONTENTS OF /opt/golang! Are you sure you want to proceed? [y/n] " -n 1 -r
echo    # (optional) move to a new line
if [[ ! $REPLY =~ ^[Yy]$ ]]
then
    exit 1
fi

## Configuration and init
DIR="/opt/golang"

# Update these as appropriate for your install 
declare -A DOWNLOADS
DOWNLOADS["go1.14.4"]="https://golang.org/dl/go1.14.4.linux-amd64.tar.gz"
DOWNLOADS["go1.13.12"]="https://golang.org/dl/go1.13.12.linux-amd64.tar.gz"

declare -A VERSIONS
# ENSURE THESE ARE THE SAME LABELS AS ABOVE!
VERSIONS["go1.14.4"]=11404
VERSIONS["go1.13.12"]=11312

# Clean-up before installing the defined versions
update-alternatives --quiet --remove-all go

# Create /opt/golang dir and download from golang downloads website
mkdir -p /opt/golang
cd /opt/golang
rm -rf /opt/golang/* # this syntax just ensures it's clear what is being rm'd 

# Loop through the various versions to install, download them, extract them
#   and move them to the right directory names, one for each version. 
for key in ${!DOWNLOADS[@]}; do
    echo Downloading version ${key}
    # clean up previous file if it exists
    rm -f ${DOWNLOADS[${key}]##*/}*
    wget ${DOWNLOADS[${key}]}
    targz_filename=${DOWNLOADS[${key}]##*/} 
    # below assume a tar.gz file 
    tar zxvf ${targz_filename}
    # mv go to the release name
    filename=${targz_filename%.*} # strips off .gz
    filename=${filename%.*} # strips off tar
    mv go ${filename%.*}
    # save space, delete the download files
    rm -f ${DOWNLOADS[${key}]##*/}*        
done

# Finally use update-alternatives to install these versions as alternatives
for key in ${!VERSIONS[@]}; do
	echo Installing golang version ${key} with alternatives priority ${VERSIONS[${key}]}
	echo update-alternatives --quiet --install /usr/local/go go ${DIR}/${key} ${VERSIONS[${key}]}
         update-alternatives --quiet --install /usr/local/go go ${DIR}/${key} ${VERSIONS[${key}]}
	
done

echo
echo "Following golang versions installed and their priorities"
update-alternatives --display go

echo
echo "Use: sudo update-alternatives --config go"
echo "To switch between golang versions"