如何用golang中的字符串制作预告片?

I'd like to make teaser by cutting first few words (divided by spaces) from arbitrary utf8 input string content. What I came up with is this:

runes := []rune(content)
teaser := string(runes[0:75]) 

The problem is that the above code cuts words in the middle. What I want is to cut at the end of (say tenth) word, in order to make pretty teasers.

How can I achieve that?

func teaser(s string, wordCount int) string {
    words := strings.Fields(s)

    if len(words) < wordCount {
        wordCount = len(words)
    }

    return strings.Join(words[:wordCount], " ")
}

... where s is your full string, and wordCount the number of words to include.

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