go build — Hands-on Tasks¶

Go 1.21+. Each task has explicit acceptance criteria.

Task 1: First binary¶

Init a module, write a main that prints something, and build it.

Acceptance criteria - [ ] go mod init example.com/app succeeds. - [ ] go build creates an executable named after the directory. - [ ] Running the executable prints your message without recompiling.

Task 2: Output control¶

Build into a specific path and name.

Acceptance criteria - [ ] go build -o bin/myapp . creates bin/myapp. - [ ] go build -o /dev/null ./... compiles all packages and leaves no artifact. - [ ] You can explain the difference between -o dir/ and -o file.

Task 3: Library vs main¶

Add a non-main package and build it.

Acceptance criteria - [ ] go build ./internal/yourpkg exits 0 and writes no file. - [ ] Introducing a type error makes that build fail.

Task 4: Inject version info¶

Add var version = "dev" and override it.

Acceptance criteria - [ ] go build -o app . && ./app prints dev. - [ ] go build -ldflags="-X main.version=1.0.0" -o app . && ./app prints 1.0.0. - [ ] go build -ldflags="-s -w" -o app . produces a noticeably smaller binary (compare ls -l).

Task 5: Cross-compile¶

Build for three platforms.

Acceptance criteria - [ ] GOOS=linux GOARCH=amd64 go build -o app-linux . succeeds. - [ ] GOOS=windows GOARCH=amd64 go build -o app.exe . succeeds. - [ ] file app-linux (or equivalent) confirms the target architecture. - [ ] go tool dist list shows the full set of valid targets.

Task 6: Reproducible build¶

Make two identical builds.

Acceptance criteria - [ ] CGO_ENABLED=0 go build -trimpath -ldflags="-s -w -buildid=" -o app1 . then the same into app2. - [ ] cmp app1 app2 reports no differences (or you explain any remaining difference). - [ ] go version -m app1 shows no leaked absolute home-directory paths.

Task 7: Static container build¶

Write a multi-stage Dockerfile producing a distroless image.

Acceptance criteria - [ ] The build stage uses CGO_ENABLED=0 go build. - [ ] The final image is distroless/static or scratch. - [ ] The container runs and the image is small (compare to a golang-based image).

Task 8: Inspect the cache¶

Observe caching behavior.

Acceptance criteria - [ ] First go build ./... is slow; immediate rebuild is near-instant. - [ ] go build -x . shows cache reuse for unchanged packages. - [ ] Changing one source file rebuilds only the affected packages (observe with -v).