Error deploying Ghost instance on gcloud

i was following this tutorial but when i deploy the app i get this error and i don't know how to solve it:

socketPath: '/cloudsql/' + process.env.INSTANCE_CONNECTION_NAME;
                                                                          ^

SyntaxError: Unexpected token ;
        at createScript (vm.js:56:10)
        at Object.runInThisContext (vm.js:97:10)
        at Module._compile (module.js:542:28)
        at Object.Module._extensions..js (module.js:579:10)
        at Module.load (module.js:487:32)
        at tryModuleLoad (module.js:446:12)
        at Function.Module._load (module.js:438:3)
        at Module.require (module.js:497:17)
        at require (internal/module.js:20:19)
        at Object.checkNodeEnvState [as nodeEnv] (/app/core/server/utils/startup-check.js:59:22)
        at Object.check (/app/core/server/utils/startup-check.js:22:14)
        at Object.<anonymous> (/app/index.js:14:46)
        at Module._compile (module.js:570:32)
        at Object.Module._extensions..js (module.js:579:10)
        at Module.load (module.js:487:32)
        at tryModuleLoad (module.js:446:12)
        at Function.Module._load (module.js:438:3)
        at Module.runMain (module.js:604:10)
        at run (bootstrap_node.js:393:7)
        at startup (bootstrap_node.js:150:9)
        at bootstrap_node.js:508:3

Local connection works and the app.yalm file seems fine to me

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