How to create a Gist via shell script?

create-gist.sh

#!/bin/bash

read -d '' PAYLOAD << EOF
{
  "description": "$1",
  "public": true,
  "files": {
    "notes.md": {
      "content": "$2"
    }
  }
}
EOF

if [[ -z $GITHUB_USER ]]; then
  echo "Variable GITHUB_USER not set."
  exit 1
fi

if [[ -z $GITHUB_TOKEN ]]; then
  echo "Variable GITHUB_TOKEN not set."
  exit 1
fi

echo "$PAYLOAD" | http --auth $GITHUB_USER:$GITHUB_TOKEN --body POST https://api.github.com/gists | 
  jq --raw-output '.html_url'

https://superuser.com/questions/1076564/sending-gist-to-github-via-curl-and-issues-with-new-lines-inside-file