Go vs Swift中的UTF8字符串长度和索引

Question

I have apps in Go and Swift which process strings, such as finding substrings and their indices. At first it worked nicely even with multi-byte characters (e.g. emojis), using to Go's utf8.RuneCountInString() and Swift's native String.

But there are some UTF8 characters that break the string length and indices for substrings, e.g. a string "Lorem

Answer 1

In Swift a Character is an “extended grapheme cluster,” and each of "