grails

also please note that the error is inside the callback function

_`// Step 2: Handle Google callback and exchange code for access token`_
`def callback(String code) {`
    `if (!code) {`
        `flash.message = "Authorization failed."`
        `redirect uri: "/login/auth"`
        `return`
    `}`

    `def accessToken = exchangeCodeForAccessToken(code)`
    `if (!accessToken) {`
        `flash.message = "Failed to retrieve access token."`
        `redirect uri: "/login/auth"`
        `return`
    `}`