[log] Add debug logging to dockerutil/env.go

[github-actions]

Changes

Adds a debug logger to internal/dockerutil/env.go to trace Docker -e flag environment variable expansion.

What was added

• Logger declaration: var logDockerutil = logger.New("dockerutil:env") following the project's pkg:filename naming convention
• 4 debug logging calls in ExpandEnvArgs:
  1. Function entry log with input arg count
  2. Per-env-var log when a variable is successfully found and expanded
  3. Per-env-var log when a referenced variable is not found in the process environment (key debugging signal)
  4. Completion log with output arg count

Why this is useful

ExpandEnvArgs is called when building Docker command arguments, converting passthrough -e VAR_NAME flags to -e VAR_NAME=value. Without logging, there's no visibility into:

• Which env vars are being passed through to Docker containers
• Which env vars are missing from the gateway process environment (a common misconfiguration)
• Whether the expansion produced the expected number of args

The "not found" log is especially valuable - it highlights env vars that are referenced in config but not set in the environment, which is a common source of unexpected Docker container behavior.

Debug usage

# Enable dockerutil debug logging
DEBUG=dockerutil:* ./awmg --config config.toml

# Example output
[dockerutil:env] Expanding env args: input_count=8
[dockerutil:env] Expanding env var: name=GITHUB_PERSONAL_ACCESS_TOKEN
[dockerutil:env] Env var not found in process environment: name=MISSING_VAR
[dockerutil:env] Env args expansion complete: output_count=9

Quality checklist

• Exactly 1 file modified
• No test files modified
• Logger declaration added following pkg:filename convention (dockerutil:env)
• Logger arguments don't compute anything or cause side effects (only passes existing variable names/counts)
• Logging messages are meaningful and helpful
• No duplicate logging with existing logs
• Import statements properly formatted with stdlib imports before external imports

Generated by Go Logger Enhancement

[Copilot]

Pull request overview

Adds debug-level tracing to internal/dockerutil/env.go so it’s easier to understand how Docker -e VAR_NAME arguments are expanded (or not) based on the gateway process environment.

Changes:

• Introduces a dockerutil:env namespaced logger for this file.
• Adds debug logs at function entry/exit and when env vars are expanded or missing.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.