How to resolve Consider preallocating (prealloc) lint?

Question

I catch Consider preallocating [to] (prealloc) this problen in golangci-lint my code is:

var to []string
for _, t := range s.To {
    to = append(to, t.String())
}

Do you have an idea to resolve this problem in lint?

Answer 1

Preallocate a slice with capacity so append() will have less (or no) copying to do:

to := make([]string, 0, len(s.To))
for _, t := range s.To {
    to = append(to, t.String())
}

Or even better, don't use append() but assign to individual slice elements:

to := make([]string, len(s.To))
for i, t := range s.To {
    to[i] = t.String()
}