Gentle Golang installation/update script - it doesn't modify existing GOPATH or binary location.

install_go.sh

#!/usr/bin/env bash

# USER DEFINED
go_version=1.12.7
go_platform=linux-amd64
go_workspace=$HOME/go # keep the workspace relative to $HOME folder
# /USER DEFINED

versioned_tarball=go${go_version}.${go_platform}.tar.gz
tmp_dir=/tmp/go_install

go_tarball=${tmp_dir}/${versioned_tarball}
go_unpacked=${tmp_dir}/go

go_binary=/usr/bin/go
# this will get pushed into .profile
go_workspace_literal='$HOME'${go_workspace//${HOME}/}


# mandatory
go_library_root=/usr/local
go_library=${go_library_root}/go
go_library_bin=${go_library}/bin

function merge_variables_with_existing_installation {
    # what if someone just added the go binary to the $PATH from the library itself?
    # e.g. $(which go) == /usr/local/go/bin/go
    # soft link that I'll perform later will fail
    if [ -x "$(command -v go)" ]; then
        go_binary=$(which go)
    fi

    if ! [ -z "$GOPATH" ]; then
        _workspace_after_home=${GOPATH//${HOME}/}
        go_workspace_literal='$HOME'${_workspace_after_home}
        eval go_workspace=${go_workspace_literal}
    else
        # if $GOPATH is not set, there is no installation
        echo 'Adding $GOPATH to ~/.profile'
        echo 'export GOPATH='${go_workspace_literal} >> ~/.profile
        echo 'export PATH=$PATH:'${go_library_bin}':$GOPATH/bin' >> ~/.profile
        source ~/.profile
    fi
}

function clear_downloads {
    # downloaded tarball exists
    if [ -f ${go_tarball} ]
    then
        rm ${go_tarball}
    fi

    # unpacked tarball exists
    if [ -d ${go_unpacked} ]
    then
        sudo rm -rf ${go_unpacked}
    fi

    rm -rf "${tmp_dir}"
}

function clear_existing_installation {
    if [ -d "${go_library}" ]
    then
        sudo rm -rf "${go_library}"
    fi

    if [ -f "${go_binary}" ]
    then
        sudo rm "${go_binary}"
    fi
}

function make_tmp_and_workspace_dirs {
    mkdir -p ${tmp_dir}
    mkdir -p ${go_workspace}/{bin,src,pkg}
}

function download_and_unpack_tarball {
    wget -O ${go_tarball} https://storage.googleapis.com/golang/${versioned_tarball}
    tar -C ${tmp_dir} -xvf ${go_tarball}
    test -d ${go_unpacked} || { echo "Go didn't unpack. Aborting."; exit 1; }
}

function change_permissions {
    # Relict, but was very often necessary for me
    sudo chown -R root:root ${go_unpacked}
    sudo chmod -R o+rw ${go_unpacked}
}

function move_libs {
    sudo mv ${go_unpacked} ${go_library_root}
}

function link_binary {
    sudo ln -s ${go_library_bin}/go ${go_binary}
}

function err_clean_up {
    clear_existing_installation
    clear_downloads
}

function perform_test {
    test_dir=${tmp_dir}/install_test
    mkdir -p ${test_dir}
    main=${test_dir}/main.go
    echo "package main">>$main
    echo "import \"fmt\"">>$main
    echo "func main() {">>$main
    echo "  fmt.Printf(\"Hello, World!\n\")">>$main
    echo "}">>$main

    go run $main
    test $? -eq 0 || { echo "Test failed. Reverting?"; err_clean_up; exit 1; }

    go version
}

###############
merge_variables_with_existing_installation
make_tmp_and_workspace_dirs
download_and_unpack_tarball
change_permissions
clear_existing_installation
move_libs
link_binary
perform_test
clear_downloads