Go have os.UserCacheDir() which added in 1.11

UserCacheDir returns the default root directory to use for user-specific cached data. Users should create their own application-specific subdirectory within this one and use that.

On Unix systems, it returns $XDG_CACHE_HOME as specified by https://specifications.freedesktop.org/basedir-spec/basedir-spec-latest.html if non-empty, else $HOME/.cache. On Darwin, it returns $HOME/Library/Caches. On Windows, it returns %LocalAppData%. On Plan 9, it returns $home/lib/cache.

If the location cannot be determined (for example, $HOME is not defined) or the path in $XDG_CACHE_HOME is relative, then it will return an error.

Go also have os.UserConfigDir() which added in 1.13

UserConfigDir returns the default root directory to use for user-specific configuration data. Users should create their own application-specific subdirectory within this one and use that.

On Unix systems, it returns $XDG_CONFIG_HOME as specified by https://specifications.freedesktop.org/basedir-spec/basedir-spec-latest.html if non-empty, else $HOME/.config. On Darwin, it returns $HOME/Library/Application Support. On Windows, it returns %AppData%. On Plan 9, it returns $home/lib.

If the location cannot be determined (for example, $HOME is not defined) or the path in $XDG_CONFIG_HOME is relative, then it will return an error.

It will be good to utilize this for config.CacheDir() and config.ConfigDir() instead of custom implementations.