This function is based on a custom OpenFaaS kotlin template, which you have to pull explicitly using:
# Run in project directory
faas-cli template pull https://github.com/s1monw1/openfaas-kotlin.git
To build the function, you can run
faas-cli build -f kkon-openweather.yml
To then deploy it, run:
faas-cli deploy -f kkon-openweather.yml
After deployment, you will be able to execute it via http://127.0.0.1:31112/function/kkon-openweather?city=Cologne