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Demo project

A small Go module that exercises most of the topics covered in this folder:

09-demo-project/
├── go.mod                          # module manifest
├── main.go                         # package main — the program entrypoint
├── counter/
│   ├── counter.go                  # public package, importable from outside
│   ├── counter_test.go             # internal tests + benchmark
│   └── testdata/                   # ignored by the build, used by tests
│       ├── alice.txt
│       └── lorem.txt
└── internal/
    └── workpool/
        └── workpool.go             # only importable from inside this module

What each part demonstrates:

  • go.mod — module path is example.com/demo; created with go mod init.
  • main.go — package main produces an executable. It imports both counter (sibling package) and uses the runtime tracer.
  • counter/ — an ordinary package, importable as example.com/demo/counter.
  • counter/counter_test.go — same-package tests (can see unexported symbols), plus a BenchmarkCountConcurrent.
  • counter/testdata/ — the go tool refuses to compile anything inside testdata/, so fixtures live here safely.
  • internal/workpool/ — Go's compiler enforces that example.com/demo/internal/workpool can only be imported by packages rooted at example.com/demo. If you copied this module to another path, external code could not reach workpool.

Running it

From this directory:

go run .

Expected output (numbers approximate):

Processed 400 jobs across 2 unique files; total words: 42000

This also writes trace.out.

Running the tests

go test ./...

To run the benchmark:

go test -bench=. ./counter

Viewing the trace

After go run . has produced trace.out:

go tool trace trace.out

This starts a local web server and prints a URL like http://127.0.0.1:NNNNN/.... Open it in a browser and explore:

  • View trace — the goroutine timeline.
  • Goroutine analysis — what each goroutine spent its time on.
  • Sync / scheduler blocking profiles — where goroutines were waiting.

Press Ctrl-C in the terminal to stop the viewer.

Files relating back to the conspect

Topic Conspect file Where you see it here
go.mod directives 04-go-file-types.md go.mod
_test.go, testdata/ 04-go-file-types.md counter/counter_test.go, counter/testdata/
internal/ rule 05-special-folders.md internal/workpool/
runtime/trace and go tool trace 03-go-tool-trace.md main.go's trace.Start / trace.Stop, plus trace.out
go run, go test, go build 02-go-subcommands.md the commands above