Fix content tests; run tests via GitHub Actions

[alexandear]

The PR fixes the test that checks code examples in the _content/tour directory and adds GitHub Actions workflow to run tests on each PR or push to the main branch.

Now, running go test -v ./... works flawlessly.

I have divided the PR into separate logical commits to facilitate review. Each commit corresponds to one logical change.

Changes:

• Fixed TestContent to work with //go:build build constraint. It's worth mentioning that the tour from Go team's uses // +build comments, but this gotour uses //go:build (introduced here drop legacy build tag #45). Thus, TestContent has been adapted to work with //go:build.
• Moved content_test.go to the root because go test skips the _content folder when detecting tests.
• Renamed TestContent to TestContentTour.
• Retained only one content_test.go that checks examples for all languages.
• Added the missing OMIT to all code snippets.
• Added the build constraint nobuild to code snippets that cannot be compiled via go build.
• Added the build constraint norun to code snippets that cannot be executed. Note that we cannot use no-run (with a hyphen) as a build constraint name.

[ardan-bkennedy]

We would need to review this together before I can accept it. I don't run any tests since the code was taken from the Go team and I don't update it. I just check the site and publish.

I'm not adverse but we will need to jump on a call.

[alexandear]

@ardan-bkennedy I updated the PR's description with extended explanation. Hope this clarifies changes a bit.

[ardan-bkennedy]

It's too big and I want to review this with you if I'm going to accept it. I'll ping you during the week

[ardan-bkennedy]

Give me a PR to the bill/testing branch please.

[alexandear]

Give me a PR to the bill/testing branch please.

Changed base branch to the bill/testing.

[alexandear]

Hello @ardan-bkennedy,
I noticed that you merged into the bill/testing branch. Is there a chance this PR will be merged into the main branch?

[ardan-bkennedy]

I could not get the tests to work. When I run go test ./... everything hangs. I have not had the time to review why.

[alexandear]

The tests are not hanging; they are just slow. I changed the test to target only the eng directory (see the PR #262), and it took 50 seconds to complete:

❯ go test ./...
?       github.com/ardanlabs/gotour/cmd/markdown-to-site        [no test files]
?       github.com/ardanlabs/gotour/cmd/tour    [no test files]
?       github.com/ardanlabs/gotour/internal/tour       [no test files]
?       github.com/ardanlabs/gotour/internal/socket     [no test files]
ok      github.com/ardanlabs/gotour     49.456s
ok      github.com/ardanlabs/gotour/internal/webtest    (cached)