🧹 chore: Add env var support to go module

[jpmcb]

Adds env vars for go module

Refs PCC-1166

[linear-code]

PCC-1166

[greptile-apps]

Greptile Summary

Adds optional environment-variable configuration to the Go module and applies each supplied KEY=VALUE entry to its build container.

• Adds an envVars constructor argument and stores it on the module.
• Validates and applies environment-variable entries when constructing the container.
• Documents command-line and toolchain customization usage.

Confidence Score: 5/5

The PR appears safe to merge, with no concrete actionable failures established in the changed code.

The environment variables are parsed as KEY=VALUE, applied to the shared Go container setup, and construction errors are propagated by both affected checks.

Important Files Changed

Filename	Overview
go/main.go	Adds optional environment-variable parsing and propagation while updating checks to handle container-construction errors.
go/README.md	Documents environment-variable usage, including an unverified toolchain customization example.

_{Reviews (1): Last reviewed commit: "🧹 chore: Add env var support to go modu..." | Re-trigger Greptile}