flatten_arrays.go

package main

import (
	"fmt"
	"reflect"
)

func flatten(v ...interface{}) {
	flatenned := flattenDeep(nil, reflect.ValueOf(v))
	fmt.Println(flatenned)
}

func flattenDeep(args []interface{}, v reflect.Value) []interface{} {
	kind := v.Kind()

	if kind == reflect.Interface {
		v = v.Elem()
		kind = v.Kind()
	}

	if kind == reflect.Array || kind == reflect.Slice {
		for i := 0; i < v.Len(); i++ {
			args = flattenDeep(args, v.Index(i))
		}
	} else {
		args = append(args, v.Interface())
	}

	return args
}

func main() {
	flatten([]interface{}{1, 2, []interface{}{3}}, []interface{}{4})
}