Switch from go-kit/log to log/slog for logging.

[woblerr]

Bumped github.com/prometheus/exporter-toolkit to v0.14.0.
Bumped github.com/prometheus/common to v0.63.0.
Bumped github.com/prometheus/client_golang to v1.20.4.
Dropped dependencies for go-kit/log and go-logfmt/logfmt. Updated other dependencies.

The logging system has been replaced with log/slog from the stdlib. This change is being made across the prometheus ecosystem. The logging output has changed, but the messages and levels remain the same. The ts label for the timestamp has between replaced with time. The caller field has been replaced by the source field. The level field now exposes the log level in capital letters.

Old log format example:

ts=2025-05-11T13:09:05.384Z caller=pgbackrest_exporter.go:97 level=info msg="Starting exporter" name=pgbackrest_exporter version=0.19.0
ts=2025-05-11T13:09:05.385Z caller=pgbackrest_exporter.go:154 level=info mgs="Use exporter parameters" endpoint=/metrics config.file=
ts=2025-05-11T13:09:05.388Z caller=tls_config.go:313 level=info msg="Listening on" address=[::]:9854
ts=2025-05-11T13:09:05.388Z caller=tls_config.go:316 level=info msg="TLS is disabled." http2=false address=[::]:9854

New log format example:

time=2025-05-11T13:32:54.939Z level=INFO source=pgbackrest_exporter.go:96 msg="Starting exporter" name=pgbackrest_exporter version=unknown
time=2025-05-11T13:32:54.940Z level=INFO source=pgbackrest_exporter.go:153 msg="Use exporter parameters" endpoint=/metrics config.file=""
time=2025-05-11T13:32:54.943Z level=INFO source=tls_config.go:347 msg="Listening on" address=[::]:9854
time=2025-05-11T13:32:54.943Z level=INFO source=tls_config.go:350 msg="TLS is disabled." http2=false address=[::]:9854

See prometheus/exporter-toolkit#240 and prometheus/common#677.

[Copilot]

Pull Request Overview

This PR replaces the legacy go-kit/log logging system with the stdlib log/slog while updating several dependency versions. Key changes include switching all logger interfaces from go-kit/log to slog, updating logger method invocations throughout the code and tests, and bumping dependency versions in go.mod.

Reviewed Changes

Copilot reviewed 337 out of 337 changed files in this pull request and generated no comments.

File	Description
pgbackrest_exporter.go	Migrated logging calls to slog and updated logger parameter types.
go.mod	Dependency versions bumped and unused logging packages removed.
Multiple backrest/*.go and corresponding tests	Replaced go-kit/log with slog across exporter, metrics, and test files.

Comments suppressed due to low confidence (3)

pgbackrest_exporter.go:31

• The update to using *slog.Logger in the API is effective, but please ensure that all interface contracts and concurrent usages are properly reviewed to avoid any race conditions in production.

func StartPromEndpoint(logger *slog.Logger) {

backrest/backrest_wal_metrics_test.go:332

• Verify that the expectation of uppercase log level strings (e.g. "level=ERROR") is consistent across all tests and logging configurations in the new slog setup.

errorsOutputCount := strings.Count(out.String(), "level=ERROR")

pgbackrest_exporter.go:80

• Ensure that the formatting and structure of slog log messages, which now output key values in uppercase by default, are consistently handled and parsed across the system, especially in log monitoring setups.

logger.Error("Get data from pgBackRest failed", "err", err)