update-go.sh

#!/usr/bin/env bash

# update-go.sh - script for automating Go update on my Debian machine
set -eu

# Constants for operations
# Make sure these don't end with a trailing slash
DOWNLOADS_DOMAIN="https://go.dev/dl"
DOWNLOAD_DIRECTORY="$HOME/downloads"
GO_INSTALL_PARENT="/usr/local"

INSTALLED_VERSION=$(go version 2>/dev/null | cut -d' ' -f3 || echo "not installed")

# Avoid destructive rm -rf later down the line
if [ -z "$GO_INSTALL_PARENT" ]; then
	echo "\$GO_INSTALL_PARENT is empty, this could be destructive - aborting!"
	exit 1
fi

# Detect system architecture
case "$(uname -m)" in
	x86_64)  go_arch="amd64" ;;
	aarch64) go_arch="arm64" ;;
	i686)    go_arch="386" ;;
	*)
		echo "Unsupported architecture: $(uname -m)"
		exit 1
	;;
esac

# Fetch data about available downloads
DOWNLOAD_DATA=$(curl -s "$DOWNLOADS_DOMAIN/?mode=json" | jq -c --arg go_arch $go_arch '.[0].files[] | select(.os == "linux" and .arch == $go_arch)')
if [ -z "$DOWNLOAD_DATA" ]; then
	echo "Error: data about available downloads is empty"
	exit 1
fi
#echo ${DOWNLOAD_DATA} > file_data.json # debug

data_filename="$(jq -r .filename <<< $DOWNLOAD_DATA)"
data_version="$(jq -r .version <<< $DOWNLOAD_DATA)"
data_hash="$(jq -r .sha256 <<< $DOWNLOAD_DATA)"

# Show version information and ask user if we should proceed
printf "Version installed: $INSTALLED_VERSION\nVersion available: $data_version\n\n"

read -rp "Continue with installing into \"$GO_INSTALL_PARENT\" [y/N]: " CONFIRM
if [ "$CONFIRM" != "y" ] && [ "$CONFIRM" != "Y" ]; then
	echo "Aborting."
	exit 0
fi

# Download the golang archive
echo "Downloading $DOWNLOADS_DOMAIN/$data_filename"
curl -sL --create-dirs -O --output-dir "$DOWNLOAD_DIRECTORY" "$DOWNLOADS_DOMAIN/$data_filename"
file_location="$DOWNLOAD_DIRECTORY/$data_filename"

# Verify whether file was downloaded successfully
echo "$data_hash  $file_location" | sha256sum --check --status || {
	echo "Error: downloaded file didn't match sha256 hash online: $data_hash"
	exit 1
}

# Unpack the downloaded archive into $GO_INSTALL_PARENT/go
echo "Removing old installation data at $GO_INSTALL_PARENT/go"
sudo rm -rf "$GO_INSTALL_PARENT/go"
echo "Unpacking new golang archive into $GO_INSTALL_PARENT"
sudo tar -C "$GO_INSTALL_PARENT" -xzf "$file_location"

echo "Finished."