How to append to slices as map values with reflection?

Assumptions

1. I'm using go1.17 not 1.18 so answers in go 1.18 may help others but not me.
2. I searched and tried many things but this scenario never solved.

Problem

import (
	"fmt"
	"reflect"
)

func main() {
	l := map[string][]interface{}{"a": {}}
	appendData(l["a"])
	fmt.Println(l["a"])
}

func appendData(k interface{}) {
	lValue := reflect.ValueOf(k)
	lValue.Set(reflect.Append(lValue, reflect.ValueOf(1)))
	lValue.Set(reflect.Append(lValue, reflect.ValueOf(2)))
	lValue.Set(reflect.Append(lValue, reflect.ValueOf(3)))
}

I simplified the scenario into this piece of code.
I just need to have the ability to change elements of that passed slice of interfaces([]interface{}) from appendData function.
Please do not send me this line of code l["a"] = appendData(l["a"]).([]interface{}).
I know that this works but I can't implement that in my code for some reason.(I'm doing some BFS stuff and I can't do this, I have to change some values at the time)

What I Want?

I just wanna see this output:

[1, 2, 3]

Is it possible?
Are there any other alternative ways that I can change those data from somewhere else in my code?
Thanks for your help.

You will never see [1, 2, 3] printed, no matter what appendData() does if only the slice is passed.

2 things: You can't change values stored in maps. If the value must be changed, you have to reassign the new value. For details see https://stackoverflow.com/questions/42716852/how-to-update-map-values-in-go/42716918#42716918

Second: you also can't change values stored in interfaces. For details, see https://stackoverflow.com/questions/47572782/removing-an-element-from-a-type-asserted-slice-of-interfaces/47572859#47572859

The right approach: if you want to change something, always pass a pointer to it, and modify the pointed value. Of course in your case you can't pass a pointer that points to a value stored in a map (that "points into the map"), so that's not possible. Map index expressions are not addressable, for details, see https://stackoverflow.com/questions/57321933/cannot-take-the-address-of-map-element/57322003#57322003. If you must use a map, you must store a pointer in the map, and you may pass that pointer.

Another approach is to return the new, modified slice and assign the new slice at the caller, exactly what / how the builtin append() does it (append() returns a new slice which you're expected to assign / store). If you go down this route, you may store non-pointer slices in the map, since you can reassign the modified slice to the same map key.