same problem, that's the only test that I couldn't pass

for each loop is doable

you both have a kind of similar solution

return the length of the string excluding alpha-numeric characters

use charAt() method

https://go.dev/doc/effective_go#mixed-caps

Finally, the convention in Go is to use MixedCaps or mixedCaps rather than underscores to write multiword names.

https://github.com/golang/go/wiki/CodeReviewComments#mixed-caps

Mixed Caps
This applies even when it breaks conventions in other languages. For example an unexported constant is maxLength not MaxLength or MAX_LENGTH.

While golint is now deprecated, it would immediately flag use of MORSE_CODE as inappropriate.

Your own link notes at the bottom:

Tutorials, references, and examples are constantly reviewed to avoid errors, but we cannot warrant full correctness of all content.

I’ll take the word of github.com/golang/go and go.dev documentation itself as more authoritative than an online “learn how to program” intro page. Even if this only concerns style recommendations of what should be prefered, not what must be done.

At most a suggestion but not an issue.

It is currently the case

Absolutely unclear issue. We cannot help. OP is probably mistaken, and is long time inactive.

This is either wrong or argued: https://www.golangprograms.com/go-language/constants.html

Duplicate issue.

This doesn't affect the coding challenge and is not an issue, at most a suggestion.

Read the description again.