Added docker login for release steps (#350)

Author: oakrizan

.buildkite/hooks/pre-command

@@ -15,7 +15,7 @@ if [[ "$BUILDKITE_PIPELINE_SLUG" == "golang-crossbuild" && ( "$BUILDKITE_STEP_KE
     export PRIVATE_CI_GCS_CREDENTIALS_SECRET=$(retry 5 vault kv get -field plaintext ${PRIVATE_CI_GCS_CREDENTIALS_PATH})
 fi
 
-if [[ ("$BUILDKITE_PIPELINE_SLUG" == "golang-crossbuild" || "$BUILDKITE_PIPELINE_SLUG" == "llvm-apple"  || "$BUILDKITE_PIPELINE_SLUG" == "fpm") && ( "$BUILDKITE_STEP_KEY" == build* ) ]]; then
+if [[ ("$BUILDKITE_PIPELINE_SLUG" == "golang-crossbuild" || "$BUILDKITE_PIPELINE_SLUG" == "llvm-apple"  || "$BUILDKITE_PIPELINE_SLUG" == "fpm") && ( "$BUILDKITE_STEP_KEY" == build* || "$BUILDKITE_STEP_KEY" == release* ) ]]; then
     export DOCKER_USERNAME_SECRET=$(retry 5 vault kv get -field user "${DOCKER_REGISTRY_SECRET_PATH}")
     export DOCKER_PASSWORD_SECRET=$(retry 5 vault kv get -field password "${DOCKER_REGISTRY_SECRET_PATH}")
     docker login -u "${DOCKER_USERNAME_SECRET}" -p "${DOCKER_PASSWORD_SECRET}" "${DOCKER_REGISTRY}" 2>/dev/null