How to do I create a separate thread to do a network operation in Android?

Question

I am trying to convert a URL to Base64 in Kotlin. I am using Apache Commons IO to accomplish this by first converting the URL to a ByteArray:

val imageBytes = IOUtils.toByteArray(URL(url))

This line creates a android.os.NetworkOnMainThreadException error when I run my app. How do I resolve this? I don't want to change the ThreadPolicy to bypass the error. Below the above line of code, I also have the following:

val imageBase64 = Base64.encode(imageBytes, Base64.URL_SAFE and Base64.NO_WRAP)

val item = ItemCard(
    imageBase64,
    label,
    total
)

list += item

The entire code block is in a loop. So I would also need something where I can get the result in a timely manner where it doesn't interfere with the actual Base64 encoding.