example code to aws-sigv4 sign custom http request with aws-sdk swift. Code doesn't compile, you should amend it a little bit

aws-sdk-swift-sigv4.swift

import SwiftUI
import AWSClientRuntime
import AWSSigner
import AWSSDKHTTPAuth
import Foundation
import AWSSDKIdentity
import SmithyHTTPAPI
import SmithyHTTPAuth
import Smithy
import AwsCommonRuntimeKit
import SmithyHTTPAuthAPI
import ClientRuntime

let credentialResolver = ProfileAWSCredentialIdentityResolver()
let identity = try await credentialResolver.getIdentity()

let url = URL(string: host)
guard
    let urlComponents = URLComponents(url: url!, resolvingAgainstBaseURL: false) else {
    return
}

let config = AWSSigningConfig(
    credentials: identity,
    expiration: 3600,
    signedBodyHeader: .contentSha256,
    signedBodyValue: .empty,
    flags: SigningFlags(
        useDoubleURIEncode: false,
        shouldNormalizeURIPath: false,
        omitSessionToken: false
    ),
    date: Date(),
    service: "service",
    region: "earth-region-1",
    signatureType: .requestHeaders,
    signingAlgorithm: .sigv4
)

let requestBuilder = HTTPRequestBuilder()
    .withMethod(.post)
    .withHost(urlComponents.host!)
    .withPath("/")
    .withPort(UInt16(exactly: urlComponents.port!)!)
    .withProtocol(URIScheme(rawValue: urlComponents.scheme!)!)
    .withHeaders(Headers(httpHeaders: [
        HTTPHeader(name: "Host", value: host),
        HTTPHeader(name: "content-type", value: "application/json"),
    ]))
    .withBody(.data(Data(payload.utf8)))

CommonRuntimeKit.initialize()

let signer = AWSSigV4Signer()
guard let signedRequest = await signer.sigV4SignedRequest(requestBuilder: requestBuilder, signingConfig: config) else {
    return
}

print(signedRequest.headers)