As for the link you mentioned:
https://authzed.com/docs/guides/first-app, when I tried to follow the code to create a client, it throws the folloing error:
$ go build -o main.go *.go
# command-line-arguments
./main.go:25:6: multiple-value grpcutil.WithSystemCerts(grpcutil.VerifyCA) (value of type (grpc.DialOption, error)) in single-value context