Fetching remote configuration on app boot (Vapor 3)

1_DispatchBox.swift

import Dispatch

// Utility class for thread-safe access to an "app global" variable
final class DispatchBox<T>: Service {
    private let queue = DispatchQueue(label: "DispatchBox_\(T.self)_Queue")
    private var _value: T?

    var value: T? {
        get { return queue.sync { self._value }}
        set { queue.async { self._value = newValue }}
    }
}

2_SampleConfiguration.swift

import Foundation

// This sample class can be used to parse a JSON like:
// { "secret": "FOOBAR" }
struct SampleConfiguration: Decodable {
    let secret: String
}

3_configure.swift

import Vapor

public func configure(_ config: inout Config, _ env: inout Environment, _ services: inout Services) throws {
    // ... other configuration ...
    
    // Creating a holder for SampleConfiguration
    let holder = DispatchBox<SampleConfiguration>()
    services.register(holder)
}

4_boot.swift

import Vapor

/// Called after your application has initialized.
public func boot(_ app: Application) throws {
    let client = try app.make(Client.self)
    let holder = try app.make(DispatchBox<SampleConfiguration>.self)

    let config = try client.get("https://api.jsonbin.io/b/5b5f00c4f24d8943d0505d0a")
        .flatMap { try $0.content.decode(SampleConfiguration.self) }
        .wait()

    holder.value = config
}

5_routes.swift

import Foundation
import Vapor

/// Register your application's routes here.
public func routes(_ router: Router) throws {
    router.get("secret") { req -> String in
        let holder = try req.make(DispatchBox<SampleConfiguration>.self)
        return holder.value?.secret ?? ""
    }
}

Thanks 👍