We want to serve files via https also for devlopment and therefore we need to create a self signed certificate. Luckily Go comes with a tool for that out of the box which we can use. In order to create these certicficates, create a tls directory in the root and execute the following command:

go run /usr/local/go/src/crypto/tls/generate_cert.go --rsa-bits=2048 --host=localhost

If you've installed Go via homebrew, you can find the generate_cert.go file under /usr/local/Cellar/go/<version>/libexec/src/crypto/tls/generate_cert.go