Base58String is based off of go-base58 string, available here.
This library provides an idiomatic Swift version of the go library.
Add the following to your Package.swift file in "dependencies".
.package(url: "https://github.com/cloutiertyler/Base58String.git", from: "0.1.0")
import Foundation
import Base58String
func test() {
let data = Data([222, 100, 50])
print("Data: \(Array(data))")
let encoded = String(base58Encoding: data)
print("Encoded string: \(encoded)")
let decoded = Data(base58Decoding: encoded)!
print("Decoded data: \(Array(decoded))")
}