Why does a Go build that works locally fail in CI when GO111MODULE is enabled?
In Go 1.16 the GO111MODULE variable defaults to on, enabling module‑aware mode even when no go.mod file is present. Locally, a writable go.mod allows go build to succeed because the tool can satisfy dependencies from the existing module file. In a CI environment the go.mod may be read‑only, missing, or the filesystem may prevent updates, causing go build to