fix: prefer cross-platform default DOCKER_HOST

[danielorbach]

Instead of blindly assuming a Linux operating system we can rely on the docker client package to tell us the appropriate default docker host.

What does this PR do?

I've changed the default DOCKER_HOST socket from its Linux value by relying on Docker's client library to supply their cross-platform values.

I chose to parse their value as a URL (I say parseURL doing the same) to separate between the schema and the path.

I was defensive because I am unfamiliar with the codebase - that's the reason for the suffix/prefix validations. Also, upon errors (url parsing, or unknown schema) I fallback to the predefined default rendering the changes of this PR a no-op.

Why is it important?

Windows users really want to use test-containers too! 🪟🐳

Before release v0.20.1 the host was not explicitly set to a default, hence it fell-back to the docker library's default anyways.

Related issues

• Closes [Bug]: Failing with "protocol not available, failed to create Docker provider" on Windows #1249

How to test this PR

I haven't been able to run all the tests because I currently use a Windows machine. However, I ran some container-based tests (that broke with release v0.20.1) on my machine and they have passed 🤗

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[mdelapenya]

Given the Docker client already does what I suggested in https://github.com/testcontainers/testcontainers-go/pull/1294/files#r1231789163, I think it's safer to honour the Docker client, as proposed in this PR.

Shaun approves 😎

[sonarcloud]

Kudos, SonarCloud Quality Gate passed!   

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[mdelapenya]

LGTM, thanks!

In the case we detected this fails once we are able to test the project on Windows workers, I'll let you know to collaborate on an eventual fix.

Thank you so much for your dedication to testcontaines-go! 💪 🚀

[mehdihadeli]

@danielorbach Hi,
thanks for the fix,
Did you publish a new package release for this fix?

[mdelapenya]

@mehdihadeli we are going to release a new version soon, hopefully at the end of this week

[mehdihadeli]

Thanks

[danielorbach]

@danielorbach Hi, thanks for the fix, Did you publish a new package release for this fix?

@mdelapenya I haven't a clue how to do this 😅

[mdelapenya]

Hey @danielorbach we core maintainers take care of the release process for the libraries, so no worries :)

In any case, I've just performed the release: https://github.com/testcontainers/testcontainers-go/releases/tag/v0.21.0