In this exercise I solve it, I gave it a test, I did the test and it was approved, I later gave it an attempt to finish the challenge but right there I get an error (I'm new to this kata thing).

kata solution != kata suggestion!

Also, do not post solution in discourse and please flag it with spoiler if you want to disclose anything related to revealing solutions directly or indirectly

please help to understand, i can't find information
why we must initialize var sum = 0;
why code can't work just like var sum

Hi and welcome to Codewars - please don't post spoilers in Discourse (your code is visible to everyone, including people who have not solved it). If you want to discuss code, you can do it the the Solutions page - or you must use a Spoiler tag.

Ok..? What's the question here?

See https://docs.codewars.com/training/troubleshooting

Golang
2022/10/11 19:23:07 [1 -2 3 4 5]
Test Failed
Log

Expected
: 28
to equal
: 13

why str.length-2?

Read this: https://docs.codewars.com/training/troubleshooting/#works-but-no

all my TDDs pass using console.log, but using return i get this error?
Testing for fixed tests
expected 28 to equal 13