How I can add Authorization please advice me thanks

[saroar]

Here my Example:
Thinking use fetchToken function and add inside Static but it give me error
APIClient.swift:30:90: error build: Function produces expected type 'String'; did you mean to call it with '()'?

//
//  APIClient.swift
//  
//
//  Created by Saroar Khandoker on 01.11.2022.
//

import Foundation
import Combine
import NWSharedModels
import URLRouting
import InfoPlist
import FoundationExtension
import Dependencies
import AppConfiguration
import KeychainClient
import Build

typealias APIClient = URLRoutingClient<SiteRoute>

private enum APIClientKey: TestDependencyKey {
    static let testValue = APIClient.failing
}

extension APIClientKey: DependencyKey {

    func fetchToken() -> String? {
        let identifier = DependencyValues._current.build.identifier
        do {
            let token = try DependencyValues._current.keychainClient.readCodable(.token, identifier, RefreshTokenResponse.self)
            return token.accessToken
        } catch {
            return nil
        }
    }

    static let liveValue: APIClient = APIClient.live(
        router: siteRouter.baseRequestData(
            .init(
                scheme: EnvironmentKeys.rootURL.scheme,
                host: EnvironmentKeys.rootURL.host,
                port: EnvironmentKeys.setPort(),
                headers: ["Authorization": ["Bearer \(fetchToken)"]]
            )
        )

//            .baseURL(DependencyValues
//            ._current
//            .appConfiguration
//            .apiURL

    )
}

extension DependencyValues {
    var apiClient: APIClient {
        get { self[APIClientKey.self] }
        set { self[APIClientKey.self] = newValue }
    }
}

enum APIError: Error {
    case serviceError(statusCode: Int, APIErrorPayload)
    case unknown

    init(error: Error) {
        if let apiError = error as? APIError {
            self = apiError
        } else {
            self = .unknown
        }
    }
}

extension APIError: Equatable {

}

struct APIErrorPayload: Codable, Equatable {
    let reason: String?
}

extension APIClient {

    @available(iOS 13, macOS 10.15, tvOS 13, watchOS 6, *)
    public func request<Value: Decodable>(
        for route: Route,
        as type: Value.Type = Value.self,
        decoder: JSONDecoder = .init()
    ) async throws -> Value {
        let (data, response) = try await self.data(for: route)

        if let statusCode = (response as? HTTPURLResponse)?.statusCode {
            switch statusCode {
            case 200 ..< 300:
                return try decoder.decode(Value.self, from: data)

            case 400 ..< 500:
                let payload = try decoder.decode(APIErrorPayload.self, from: data)
                throw APIError.serviceError(statusCode: statusCode, payload)

            default:
                throw APIError.unknown
            }
        } else {
            throw APIError.unknown
        }
    }
}