Google Cloud IoT Core & Golang

gcpiot_startup.sh

echo "Installing Mosquitto (MQTT) client tools"
opkg update > /dev/null
opkg install mosquitto mosquitto-client > /dev/null

echo "Configure GCP Cloud IoT"
SERVICE_ENDPOINT="mqtt.googleapis.com:8883"
read -p "GCP Project ID     : " PROJECT
read -p "GCP Region         : " REGION
read -p "GCP IoT Registry ID: " REGISTRY
read -p "GCP IoT Device ID  : " DEVICE

LONG_REGISTRY=projects/${PROJECT}/locations/${REGION}/registries/${REGISTRY}

echo "Generate JWT good for 24 hours"
PASSWORD=$(\
  ./makejwt \
  --duration=24 \
  --project=${PROJECT} \
  --private_key=./${DEVICE}.key.pem)

echo "Publish test message to Cloud IOT"
mosquitto_pub \
--host mqtt.googleapis.com \
--port 8883 \
--id ${LONG_REGISTRY}/devices/${DEVICE} \
--username unused \
--pw ${PASSWORD} \
--cafile /roots.pem \
--tls-version tlsv1.2 \
--protocol-version mqttv311 \
--debug \
--qos 1 \
--topic /devices/${DEVICE}/events \
--message "Hello Henry!"

@DazWilkin,
Could you please provide makejwt?
Thanks in advance!