[golangBuild] Add better error logging to isMainPackage

[LukasHeimann]

In my project, i try to use the packages setting to build multiple binaries at the same time:

  golangBuild:
    output: i2-automated-pipelines-test
    privateModules: "github.tools.sap/*"
    packages:
      - ./cmd/run1
      - ./cmd/run2

This triggers a code path leading to isMainPackage. Unfortunately, inside all of this, the go binary fails with exit code 1:

info  golangBuild - running command: go list -f {{ .Name }} ./cmd/run1
fatal golangBuild - execution of golang build failed - failed to calculate output binaries or directory, error: running command 'go' failed: cmd.Run() failed: exit status 1

It must be exactly the go command inside isMainPackage, because in the loop to get the output paths, no other go binary is executed, and my second package (run2) is not logged.

When I run the command go list -f "{{ .Name }}" ./cmd/run1 locally, I don't get any error, the command outputs main instead -- which is the non failure path.

Unfortunately, when the go binary fails in this case, we don't see any error output, as console output is entirely redirected to outBuffer, which is not returned.

This PR improves this by using fmt.Errorf to attach the outBuffer to the error. Using %w to wrap the original error, any introspection using errors.Is and errors.As would still work (although noone seems to do this). I also made sure to only add the additional context of the error output after the original error, so the current error message stays unchanged -- there is just more context at the end of it.

Please consider merging this change to improve the error output.

[valfz]

/it-go

[ashlymat]

@LukasHeimann Thanks for the PR.
Is it possible to add a small unit test?

[LukasHeimann]

@ashlymat Done! I hope, this is what you expected -- a small test specifically targeting the (changed) error message.

Not sure why the sonar bot is not picking up the new coverage, though -- I very explicitly test the string concatenation handling in the changed function...

[Googlom]

/it-go

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

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