You can achieve the same effect without a function though: just create a local copy and use the address of that:

for _, each := range arr {
    each2 := each
    err := ds.repo.Insert(&each2)
    // ...
}

Also note that you may also store the address of the slice elements:

for i := range arr {
    err := ds.repo.Insert(&arr[i])
    // ...
}

Solve “using a reference for the variable on range scope `xxxx` (scopelint)” error.

int to string

s := strconv.Itoa(123)

int64 to string

var n int64 = 123
s := strconv.FormatInt(n, 10) // s == "123" (decimal)

var n int64 = 123
s := strconv.FormatInt(n, 16) // s == "7b" (hexadecimal)

string to int

s := "123"
n, err := strconv.Atoi(s)

string to int64

s := "123"
n, err := strconv.ParseInt(s, 10, 64)