Goで2つのSlice(A、B)のうち、Aにだけ存在し、Bには存在しない値を持ったSliceを生成する ref: https://qiita.com/Sekky0905/items/1afa6a78f0aa7354f290

file0.go

s1 := []int{1, 2, 3, 4}
s2 := []int{1, 5, 6, 7}

file1.go

package main

import "fmt"

func main() {
    slice1 := []int{1, 2, 3, 4}
    slice2 := []int{1, 5, 6, 7}
    newSliceA := CheckNumIncludedOnlyOneSide(slice1, slice2)
    fmt.Printf("sliceA = %#v\n", newSliceA)

    slice3 := []int{1, 2, 3, 4}
    slice4 := []int{5, 6, 7, 8}
    newSliceB := CheckNumIncludedOnlyOneSide(slice3, slice4)
    fmt.Printf("sliceB = %#v\n", newSliceB)

    slice5 := []int{1, 2, 3, 4, 4, 4, 4, 4}
    slice6 := []int{1, 1, 5, 6, 7}
    newSliceC := CheckNumIncludedOnlyOneSide(slice5, slice6)
    fmt.Printf("sliceC = %#v\n", newSliceC)

    slice7 := []int{1, 2, 3, 4}
    slice8 := []int{1, 2, 5, 6, 7}
    newSliceD := CheckNumIncludedOnlyOneSide(slice7, slice8)
    fmt.Printf("sliceD = %#v\n", newSliceD)

}

// CheckNumIncludedOnlyOneSide は、sliceAには含まれているが、sliceBには含まれていない値を持ったsliceを返す
func CheckNumIncludedOnlyOneSide(sliceA, sliceB []int) []int {
    newSlice := []int{}
    for _, a := range sliceA {
        // 重複してるかどうかのフラグ
        isDuplicated := false
        for _, b := range sliceB {
            if a == b { // sliceAとsliceBの要素が同じものだったら、フラグをtrueに
                isDuplicated = true
            }
        }

        if !isDuplicated { // フラグをfalseのものは、newSliceに追加
            newSlice = append(newSlice, a)
        }
    }
    return newSlice
}

file2.txt

sliceA = []int{2, 3, 4}
sliceB = []int{1, 2, 3, 4}
sliceC = []int{2, 3, 4, 4, 4, 4, 4}
sliceD = []int{3, 4}