go mod — Hands-on Tasks¶

Go 1.21+. Each task has explicit acceptance criteria.

Task 1: Create and inspect a module¶

Initialize a module and read its files.

Acceptance criteria - [ ] go mod init example.com/lab creates go.mod with a module and go directive. - [ ] You can explain what the module path is used for.

Task 2: Add a dependency¶

Import an external package and tidy.

Acceptance criteria - [ ] Importing github.com/google/uuid and running go mod tidy adds a require line and go.sum entries. - [ ] go run . builds using the dependency. - [ ] git status shows go.mod and go.sum modified.

Task 3: tidy adds and removes¶

Observe tidy in both directions.

Acceptance criteria - [ ] Removing the import and running go mod tidy removes the require line. - [ ] Adding it back and tidying restores it. - [ ] On a clean tree, go mod tidy then git diff shows no changes (the cleanliness invariant).

Task 4: Explain the graph¶

Use graph and why.

Acceptance criteria - [ ] go mod graph prints dependency edges. - [ ] go mod why github.com/google/uuid prints the import chain. - [ ] go list -m all shows the selected version of every module.

Task 5: Verify and download¶

Exercise integrity and caching commands.

Acceptance criteria - [ ] go mod download populates the module cache. - [ ] go mod verify reports all modules verified. - [ ] You locate the cache at go env GOMODCACHE.

Task 6: Local replace for development¶

Develop against a local copy of a module.

Acceptance criteria - [ ] go mod edit -replace=example.com/dep=../dep adds a replace directive. - [ ] Builds use the local copy. - [ ] go mod edit -dropreplace=example.com/dep removes it; you note why replaces must not be merged.

Task 7: MVS in action¶

See Minimal Version Selection pick a version.

Acceptance criteria - [ ] Require an old version of a dependency, add another dependency that needs a newer version of the same module, and go list -m shows the higher one selected. - [ ] You explain why MVS chose that version.

Task 8: Vendor a module¶

Create and use a vendor directory.

Acceptance criteria - [ ] go mod vendor creates vendor/ with dependency sources. - [ ] go build -mod=vendor ./... builds from vendor/. - [ ] After a dependency change, go mod vendor keeps it in sync and git diff vendor shows the update.