Service binary on macOS prints output to stderr since 1.2.100

[Christoph Kührer]

Problem

We updated the Fiskaly service binary (from https://developer.fiskaly.com/downloads) from 1.2.000 to 1.2.100 and it looks like it's behavior on macOS changed.

When running 1.2.000 (com.fiskaly.service-darwin-amd64-v1.2.000) the log output is sent through stdout
When running 1.2.100 (com.fiskaly.service-darwin-amd64-v1.2.100) the output gets sent through stderr

We are using stderr output as an indication that something failed while starting the Fiskaly service.

Reproduction steps
This can be tried out by prefixing the console output using stdout or stderr like this:

➜  bin git:(fiskaly-update) ✗ ./com.fiskaly.service-darwin-amd64-v1.2.000 2> >(sed 's/^/stderr: /') > >(sed 's/^/stdout: /')
stdout: http service listening on :8080

➜  bin git:(fiskaly-update) ✗ ./com.fiskaly.service-darwin-amd64-v1.2.100 2> >(sed 's/^/stderr: /') > >(sed 's/^/stdout: /')
stderr: 2020/11/24 11:28:04 main.go:35: http service listening on :8080

Expected outcome
Regular logging/info output is printed through stdout for regular output and to stderr for errors.