Add pointer concept

[andrerfcsantos]

Fixes #1643

[ErikSchierboom]

I'm really impressed with this PR! You did an excellent job. I've left some minor comments.

I don't really know anything about Go, so I'll leave it to others to review the Go parts of the code.

[iHiD]

I've reviewed the introduction.md - It's really great 🙂

[andrerfcsantos]

Thanks @iHiD and @ErikSchierboom for the extensive review!

These are great suggestions, really appreciate it. At a quick glance, I agree with all of them. I'll go through them in detail and submit a new patch.

[iHiD]

@andrerfcsantos I don't think I've ever seen Erik as impressed with a first-pass of a totally new exercise before 👏

[andrerfcsantos]

Changes applied. Ready for further review!

[iHiD]

Great! I probably won't have time to review again before GoBridge launches, so if you're happy with the changes you've applied, I am too :)

I guess we just need a review on the Go side of things and then we can merge :)

[ErikSchierboom]

@iHiD Yep! Let's wait for a proper Go review, but I'll give it my approval to show the other reviewers I like this PR!

[bobahop]

Great work!

A couple of things.

For pointer to a slice, if the slice is appended to in a function it was passed into, the change will not be seen in the original, since the length and maybe capacity will change, but the pointer is only for the address. So in that way a slice does not behave the same as a map. I only mention because they are grouped together in the explanation, and it mentions that map changes will be seen in the original.

The other issue is maybe to caveat against something like

*p = &a

I want to say I read somewhere that it's a common mistake for newer programmers to use the dereference operator when reassigning a pointer to a new address.

[junedev]

Great work! Really well done! 👏
Left some minor suggestions, if you like them they probably need to be applied in all the places.

[andrerfcsantos]

Made the suggested changes.

In addition I also made other improvements:

• In the pointer arithmetic example I declared the variables using the long form instead of the shorthand syntax. This is to 1) make the types of each variable more explicit 2) be more consistent with the rest of the examples
• I modified the map example slightly to increment a value on an existing map instead of adding a new key. This is just to be closer to what the student will be required to do in the exercise.