idk man

key.sh

#!/usr/bin/env bash

KEY="SOMETHING-$(date -u +%Y-%m-%dT%H:%M:%SZ)"
ACCOUNT_KEY="SOMETHING-ELSE"

# sign <key> <account key>
function sign(){
  b64_key=$(echo -n "$2" | base64)
  payload=$(echo -n "$1" | openssl sha256 -hmac "$b64_key")

  echo -n "$payload" | base64
}

echo key: "$KEY"
echo accountkey: "$ACCOUNT_KEY"

signed=$(sign "$KEY" "$ACCOUNT_KEY")
echo signed: "$signed"