regex.Split but keep separator

[abcdef (J. T.)]

Hello,
I’m splitting txt parts by regex, the issue is thag reg.Split removes the separator.
Is there better way (more efficient) to keep it than this?

reg := regexp.MustCompile(`(?m)^\[\d+:\d+:\d+]`)

split := reg.Split(string(log), -1)

var test []string

for index, line := range split {
    submatch := reg.FindAllStringSubmatch(string(log), -1)
    submatch2 := submatch[index][0]

    test = append(test, submatch2 + line)
}

Because if I’m not wrong, it do “regexing” 2 times which is bad because I need it to be fast as possible

[skillian (Sean Killian)]

@abcdef Can you provide some example input text and desired output text?

[abcdef (J. T.)]

Here is the code example: Go Playground - The Go Programming Language

Desired output is “[HH:mm:ss] something[num]” instead of just “something[num]”

[skillian (Sean Killian)]

You’re getting just “something[num]” because you’re using (*Regexp).Split which finds the pattern you specify and splits a string every time it finds that text, just like strings.Split. You say you want “[HH:mm:ss] something[num]”, but the source text is already formatted that way, so why are you parsing it just to put it back into that format?

[christophberger]

@abcdef - So you have input that comes in linewise –

[01:00:00] something1
[02:00:00] something2
[03:00:00] something3
[04:00:00] something4

– and want to put each line into a slice field?

If you include the rest of the line in the regex (.*$) and use FindAllString instead of Split (Playground, you get a slice of [HH:mm:ss] something[num] values back.

[[01:00:00] something1 [02:00:00] something2 [03:00:00] something3 [04:00:00] something4]

Is this the output you are looking for?