Speed up goenv init by caching it

cached-goenv-init.sh

#!/bin/sh

# Running "eval $(goenv init -)" can take more than 100ms on a recent Macbook, most of that time spent
# on generating the commands, rather than evaluating them. But those commands are the same every time,
# so this generates those once, and caches it to disk. It doesn't check for freshness though, so it is 
# prudent to delete ~/.goenv.cached.init.sh after updating goenv.

# To use: replace the call to "eval $(goenv init -)" with the following code

_cached_goenv_init() {
        local goenv_init_sh=$HOME/.goenv.cached.init.sh

        if [ ! -x "$goenv_init_sh" ]; then
                echo "$goenv_init_sh, caching \"goenv init -\""
                local goenv_version=$(git -C $(dirname $(realpath $(command -v goenv))) rev-parse HEAD)
                echo "# cached for goenv $goenv_version" > $goenv_init_sh
                goenv init - --no-rehash | head -n -1 >> $goenv_init_sh
                goenv sh-rehash --only-manage-paths >> $goenv_init_sh
                chmod +x $goenv_init_sh
        fi

        . $goenv_init_sh
}

_cached_goenv_init