go_install.sh

#!/bin/bash

set -e
set -o pipefail

GO_VERSION=1.17.7
GO_PATH=/usr/local/bin/go
GOFMT_PATH=/usr/local/bin/gofmt
MODE=$1

if [ "$MODE" != "install" -a "$MODE" != "uninstall" -a "$MODE" != "switch" -a "$MODE" != "list"  ]; then
    echo "Usage: go_install.sh [install|uninstall|switch|list]"
    exit 1
fi


install() {

	if [ -n "$1" ]; then
		GO_VERSION=$1
	fi

	DOWNLOAD_URL="https://go.dev/dl/go${GO_VERSION}.linux-amd64.tar.gz"
	SAVE_DIR="/usr/local/go-${GO_VERSION}"

	if [ -d $SAVE_DIR ]; then
		echo "go $GO_VERSION is already installed."
		exit 1
	fi

	curl -sL $DOWNLOAD_URL -o - | tar -C /usr/local -xzf -
	mv /usr/local/go $SAVE_DIR

	if [ $(go_list | wc -l) -eq 1 ]; then
		switch $GO_VERSION
	fi
}

switch() {

	if [ -n "$1" ]; then
		GO_VERSION=$1
	fi
	if [ $GO_VERSION = $(go_current) ]; then
		echo "current go version is $GO_VERSION."
		exit 1
	fi
	SAVE_DIR="/usr/local/go-${GO_VERSION}"
	ln -sf $SAVE_DIR/bin/go /usr/local/bin/go
	ln -sf $SAVE_DIR/bin/gofmt /usr/local/bin/gofmt
}

uninstall() {

	if [ -n "$1" ]; then
		GO_VERSION=$1
	fi
	SAVE_DIR="/usr/local/go-${GO_VERSION}"

	if [ ! -d $SAVE_DIR ]; then
		echo "go $GO_VERSION is not exists."
		exit 1
	fi


	NUM=$(go_list | wc -l)

	rm -frv $SAVE_DIR

	if [ $NUM -eq 1 ]; then
		rm -f /usr/local/bin/go /usr/local/bin/gofmt
	else
		switch $(go_list | head -1)
	fi
}

list() {

	current=$(go_current)
	if [ $current = "none" ]; then
		echo "go is not installed."
		exit
	fi
	for go in $(go_list); do

		if echo $go | grep -q $current; then
			echo "$go (current)"
		else
			echo $go
		fi
	done
}


go_list() {

	for d in $(ls -1dv /usr/local/go-* | sort -r); do
		echo $d | sed -e 's|^/usr/local/go-||'
	done
}

go_current() {

	if [ -L $GO_PATH ]; then
		realpath=$(readlink $GO_PATH)
		if [ -x $realpath ]; then
			$GO_PATH version | sed -e 's/^go version go\(.*\) .*$/\1/'
		else
			echo "none"
		fi
	else
		echo "none"
	fi
}

case "$MODE" in
    "install" )
        install $2;;
    "uninstall" )
        uninstall $2;;
    "switch" )
        switch $2;;
    "list" )
        list ;;
    * ) break ;;
esac