Every time the directory is changed in zsh, set $GOPATH (and additions to $PATH) by recursing up through parent directories, looking for a .gopath file

zsh-gopath-search.sh

# Each time we change directory, look for some files that alter environment
# variables.
chpwd() {
    emulate -L zsh

    dir="$(pwd)"
    while [[ "$dir" == "$HOME"* ]]
    do
        if [[ -f "${dir}/.gopath" ]]
        then
            newGOPATH="${newGOPATH}:${dir}"
        fi
        dir=$(dirname "${dir}")
    done

    if [[ "$newGOPATH" != "$GOPATH" ]]
    then
        pathReplace='s|\(:[^:]*\)|\1/bin|g'
        newPathAppend=$(echo "${newGOPATH}" | sed "${pathReplace}")
        if [[ $? -ne 0 ]]
        then
            echo "Replacement failed using: echo '${newGOPATH}' | sed '${pathReplace}'"
            return
        fi
        oldPathAppend=$(echo "${GOPATH}" | sed "${pathReplace}")
        if [[ $? -ne 0 ]]
        then
            echo "Replacement failed using: echo '${GOPATH}' | sed '${pathReplace}'"
            return
        fi
        newPATH=$(echo "${PATH}" | sed "s|${oldPathAppend}\$|${newPathAppend}|")
        if [[ $? -ne 0 ]]
        then
            echo "Replacement failed using: echo '${PATH}' | sed 's|${oldPathAppend}\$|${newPathAppend}|'"
            return
        fi
        export PATH="${newPATH}"
        if [[ "${newGOPATH}" != "" ]]
        then
            export GOPATH="${newGOPATH}"
        else
            unset GOPATH
        fi
    fi
}