golang替换字符串区分大小写

test := "a,b,c,d,e"
    aaa := test
    keywordSlice := strings.Split(test,",")
    for _,v := range keywordSlice{
        reg := regexp.MustCompile("(?i)"+v)
        aaa = reg.ReplaceAllString(aaa,"<b class='f-red'>"+strings.ToUpper(v)+"</b>")
        fmt.Println(aaa)
    }

<b class='f-red'>A</b>,b,c,d,e
<<b class='f-red'>B</b> class='f-red'>A</<b class='f-red'>B</b>>,<b class='f-red'>B</b>,c,d,e
<<b <b class='f-red'>C</b>lass='f-red'>B</b> <b class='f-red'>C</b>lass='f-red'>A</<b <b class='f-red'>C</b>lass='f-red'>B</b>>,<b <b class='f-red'>C</b>lass='f-red'>B</b>,<b class='f-red'>C</b>,d,e
<<b <b class='f-re<b class='f-red'>D</b>'>C</b>lass='f-re<b class='f-red'>D</b>'>B</b> <b class='f-re<b class='f-red'>D</b>'>C</b>lass='f-re<b class='f-red'>D</b>'>A</<b <b class='f-re<b class='f-red'>D</b>'>C</b>lass='f-re<b class='f-red'>D</b>'>B</b>>,<b <b class='f-re<b class='f-red'>D</b>'>C</b>lass='f-re<b class='f-red'>D</b>'>B</b>,<b class='f-re<b class='f-red'>D</b>'>C</b>,<b class='f-red'>D</b>,e
<<b <b class='f-r<b class='f-red'>E</b><b class='f-r<b class='f-red'>E</b>d'>D</b>'>C</b>lass='f-r<b class='f-red'>E</b><b class='f-r<b class='f-red'>E</b>d'>D</b>'>B</b> <b class='f-r<b class='f-red'>E</b><b class='f-r<b class='f-red'>E</b>d'>D</b>'>C</b>lass='f-r<b class='f-red'>E</b><b class='f-r<b class='f-red'>E</b>d'>D</b>'>A</<b <b class='f-r<b class='f-red'>E</b><b class='f-r<b class='f-red'>E</b>d'>D</b>'>C</b>lass='f-r<b class='f-red'>E</b><b class='f-r<b class='f-red'>E</b>d'>D</b>'>B</b>>,<b <b class='f-r<b class='f-red'>E</b><b class='f-r<b class='f-red'>E</b>d'>D</b>'>C</b>lass='f-r<b class='f-red'>E</b><b class='f-r<b class='f-red'>E</b>d'>D</b>'>B</b>,<b class='f-r<b class='f-red'>E</b><b class='f-r<b class='f-red'>E</b>d'>D</b>'>C</b>,<b class='f-r<b class='f-red'>E</b>d'>D</b>,<b class='f-red'>E</b>