key="YOUR_API_KEY"
secret="YOUR_API_SECRET"
host="https://api.gateio.ws"
prefix="/api/v4"
method="POST"
url="/withdrawals"
query_param=""
body_param='{"withdraw_order_id":"order_123456","currency":"USDT","address":"1HkxtBAMrA3tP5ENnYY2CZortjZvFDH5Cs","amount":"222.61","memo":"","chain":"TRX"}'
timestamp=$(date +%s)
body_hash=$(printf "$body_param" | openssl sha512 | awk '{print $NF}')
sign_string="$method\n$prefix$url\n$query_param\n$body_hash\n$timestamp"
sign=$(printf "$sign_string" | openssl sha512 -hmac "$secret" | awk '{print $NF}')

full_url="$host$prefix$url"
curl -X $method $full_url -d "$body_param" -H "Content-Type: application/json" \
    -H "Timestamp: $timestamp" -H "KEY: $key" -H "SIGN: $sign"