bash defer function - just like go's defer()

defer.sh

function _run_deferred() {
  local _depth="$BASHPID.${#FUNCNAME[@]}"
  [[ "$_depth" != "$_deferred_depth" ]] && return
  local opt=$-
  set +e
  for (( i=${#_deferred[@]} - 1; i >= 0; i-- )); do
    eval "${_deferred[i]}"
  done
  [[ "$opt" == *e* ]] && set -e
}
function _defer() {
  _deferred_depth="$BASHPID.${#FUNCNAME[@]}"
  _deferred+=( "$(printf '%q ' "$@")" )
}
# This has to be an alias so that the `trap ... RETURN` runs appropriately.
shopt -s expand_aliases
alias defer='declare -a _deferred; declare _deferred_depth; trap _run_deferred EXIT RETURN; _defer'

example.sh

function foo1() { echo foo1; }
function foo2() { defer echo foo2; foo1; }
function foo3() { foo2; }
function foo4() { echo foo4-begin; ( defer echo foo4-subshell; foo3; ); echo foo4-end; }
foo4

output

foo4-begin
foo1
foo2
foo4-subshell
foo4-end