Failed to turn hex key into binary

[s8sg]

I'm trying to using the Dockerfile to run nginx

My configuration is

        auth_jwt_enabled on;
        auth_jwt_key superSecretSharedSigningKey; 
        auth_jwt_algorithm HS256;    #  using HMAC for signing 
        auth_jwt_validate_email off;

I'm using the jwt builder from: http://jwtbuilder.jamiekurtz.com/

On request I'm getting the below error

[error] 7#0: *6 failed to turn hex key into binary, client: 10.255.0.2, server: , request: "GET /api/platform/tool/userauth/user/add HTTP/1.1", host: "localhost:8080"

[s8sg]

I was clearly not paying attention, I figured out the JWT key is invalid and should be in Hex format.