Fixed docker command in get started doc

[atilbian]

What?

It fixes the docker command listed in the Get started documentation following #1536

Checklist

• I have used a meaningful title for the PR.
• I have described the changes I've made in the "What?" section above.
• I have performed a self-review of my changes.
• I have run the npm start command locally and verified that the changes look good.

• I have made my changes in the docs/sources/k6/next folder of the documentation.
• I have reflected my changes in the docs/sources/k6/v{most_recent_release} folder of the documentation.
• I have reflected my changes in the relevant folders of the two previous k6 versions of the documentation (if still applicable to previous versions).

Related PR(s)/Issue(s)

• Closes Document usage of k6 new command when used in the context of Docker #1536

[heitortsergent]

@atilbian thanks for opening the PR! It looks good to me, I'll wait for one of the other reviews to take a look as well before merging this. 🙇

[codebien]

Suggested change

	$ docker run --rm -i --user $UID -v $PWD:/app -w /app grafana/k6 new
	$ docker run --rm -i --user $UID -v $PWD:/app -w /app grafana/k6 new

This is bash dependent, should we use instead $(id -u)? @oleiade Does it work for you on fish?

[oleiade]

Good point. In fish I have to quote "$ENV_VARIABLE", but --user "$UID" does work. Let's not bother too much about fish because it has its set of differences with standard shells like $(id -u) would be (id -u) anyway.

I do think switching to $(id -u) to be a good idea nonetheless anyway 👍🏻 (fish users will know what to do about it 🙇🏻

[codebien]

Hey @atilbian,
as for the discussion before I would go with the following command:

$ docker run --rm -u $(id -u) -v $PWD:/app -w /app grafana/k6 new

it includes the following improvements:

• It removes the -i flag that isn't relevant for this command
• It uses the $(id -u) as we discussed in the dedicated discussion
• It uses the compact version of the --user flag

[CLAassistant]

All committers have signed the CLA.

[codebien]

@atilbian thanks for your contribution 🙇