Permission issues while docker push

I'm trying to push my docker image to google container image registry but get an error which says I do not have the needed permission to perform this operation.

I have already tried gcloud auth configure-docker but it doesn't work for me.

I first build the image using: docker build -t gcr.io/trynew/hello-world-image:v1 .

Then I'm trying to attach a tag and push it: docker push gcr.io/trynew/hello-world-image:v1

This is my output :

    The push refers to repository [gcr.io/trynew/hello-world-image]

    e62774cdb1c2: Preparing 
    0f6265b750f3: Preparing 
    f82351274ce3: Preparing 
    31a16430afc8: Preparing 
    67298499a3ed: Preparing 
    62d5f39c8fe4: Waiting 
    9f8566ee5135: Waiting 
    unauthorized: You don't have the needed permissions to perform this
    operation, and you may have invalid credentials. 
    To authenticate your request, follow the steps in: 
https://cloud.google.com/container-registry/docs/advanced-authentication

Google cloud services have specific information how to grant permissions for docker push, this is the first thing you should have a look I think, https://cloud.google.com/container-registry/docs/access-control

After checking that you have sufficient permissions you should proceed with authentication with something like:

gcloud auth configure-docker

See more here: https://cloud.google.com/container-registry/docs/pushing-and-pulling

If you are running docker as root (i.e. with sudo docker), then make sure to configure the authentication as root. You can run for example:

sudo -s
gcloud auth login
gcloud auth configure-docker

...that will create (or update) a file under /root/.docker/config.json.

(Are there any security implications of gcloud auth login as root? Let me know in the comments.)