Example on running Skaffold with GITLAB CI for Kubernetes in GKE (Make sure you modify it appropriately and set GCP_SERVICE_KEY and GCP_PROD_SERVICE_KEY variable in Gitlab with the service account json value)

.gitlab-ci.yml

services:
    - docker:dind

stages:
    - development
    - production

variables:
    DOCKER_DRIVER: overlay2
    DOCKER_TLS_CERTDIR: ''
    DOCKER_HOST: tcp://docker:2375

development:
    image:
        name: gcr.io/k8s-skaffold/skaffold:latest
    stage: development
    script:
        - echo "$GCP_SERVICE_KEY" > gcloud-service-key.json
        - gcloud auth activate-service-account --key-file gcloud-service-key.json
        - gcloud config set project project-dev
        - gcloud config set compute/zone asia-south1-a
        - gcloud container clusters get-credentials cluster-dev
        - kubectl config get-contexts
        - skaffold run
    only:
        - master
production:
    image:
        name: gcr.io/k8s-skaffold/skaffold:latest
    stage: production
    script:
        - echo "$GCP_PROD_SERVICE_KEY" > gcloud-service-key.json
        - gcloud auth activate-service-account --key-file gcloud-service-key.json
        - gcloud config set project project-prod
        - gcloud config set compute/zone asia-south1-a
        - gcloud container clusters get-credentials cluster-prod
        - kubectl config get-contexts
        - skaffold run -p production
    only:
        - production