{"error":"invalid_grant", "error_description": "Invalid authorization code"} with example GO code

I am using the example auth0 golang web app to log in. I receive the code back and using the curl to retrieve the authorization token with this :
curl --request POST
–url ‘https://dev-qe7ly116.us.auth0.com/oauth/token
–header ‘content-type: application/x-www-form-urlencoded’
–data grant_type=authorization_code
–data ‘client_id=Valid id’
–data ‘client_secret=valid secret’
–data ‘code=valid code’ \
–data ‘redirect_uri=http://localhost:3000/callback
secret and client ID have been changed to protect the innocent. The time between receiving the code and submitting this is less than 1 minute.

Any help would be appreciated.

Thanks in advance.