func newSignV4ChunkedReader(req *http.Request, trailer bool) (io.ReadCloser, APIErrorCode) {
	cred, seedSignature, region, seedDate, errCode := calculateSeedSignature(req, trailer)
	if errCode != ErrNone {
		return nil, errCode
	}

	if trailer {
		// Discard anything unsigned.
		req.Trailer = make(http.Header)
		trailers := req.Header.Values(awsTrailerHeader)
		for _, key := range trailers {
			req.Trailer.Add(key, "")
		}

      .build()

  @Test
  fun trailersHttp1() {
    trailers(Protocol.HTTP_1_1)
  }

  @Test
  fun trailersHttp2() {
    trailers(Protocol.HTTP_2)
  }

  private fun trailers(protocol: Protocol) {
    enableProtocol(protocol)

    server.enqueue(
      MockResponse
        .Builder()
        .addHeader("h1", "v1")
        .trailers(headersOf("t1", "v2"))
        .body(protocol, "Hello")

  private fun serverTruncatesRequestButTrailersCanStillBeRead(http2: Boolean) {
    val mockResponse =
      MockResponse
        .Builder()
        .doNotReadRequestBody()
        .trailers(headersOf("caboose", "xyz"))

    // Trailers always work for HTTP/2, but only for chunked bodies in HTTP/1.
    if (http2) {
      mockResponse.body("abc")
    } else {
      mockResponse.chunkedBody("abc", 1)
    }

    throwing in 5.0.0, we inadvertently removed the ability for callers to peek the trailers
    (by catching the `IllegalStateException` if they weren't available). This new API restores that
    capability.

 *  Fix: Don't crash on `trailers()` if the response doesn't have a body. We broke [Retrofit] users

          else -> {
            val responseBody = exchange.openResponseBody(response)
            response
              .newBuilder()
              .body(responseBody)
              .trailers(
                object : TrailersSource {
                  override fun peek() = exchange.peekTrailers()

                  override fun get(): Headers {
                    val source = responseBody.source()

        .exhaustResponse()
    server.enqueue(
      MockResponse
        .Builder()
        .clearHeaders()
        .addHeader("h1", "v1")
        .addHeader("h2", "v2")
        .trailers(headersOf("trailers", "boom"))
        .socketHandler(body)
        .build(),
    )
    val call =
      client.newCall(
        Request
          .Builder()
          .url(server.url("/"))
          .build(),

    var trailers: Headers = mockResponse.trailers
    mockResponse = mockResponse.clearHeaders()
    mockResponse = mockResponse.addHeader("")
    mockResponse = mockResponse.addHeader("", "")
    mockResponse = mockResponse.addHeaderLenient("", Any())
    mockResponse = mockResponse.setHeader("", Any())
    mockResponse.headers = headersOf()
    mockResponse.trailers = headersOf()

        !"Proxy-Authenticate".equals(fieldName, ignoreCase = true) &&
        !"Proxy-Authorization".equals(fieldName, ignoreCase = true) &&
        !"TE".equals(fieldName, ignoreCase = true) &&
        !"Trailers".equals(fieldName, ignoreCase = true) &&
        !"Transfer-Encoding".equals(fieldName, ignoreCase = true) &&
        !"Upgrade".equals(fieldName, ignoreCase = true)

    /**

      MockResponse
        .Builder()
        .clearHeaders()
        .addHeader("h1", "v1")
        .addHeader("h2", "v2")
        .chunkedBody("HelloBonjour", 1024)
        .trailers(headersOf("trailers", "boom"))
        .build(),
    )
    val call = client.newCall(Request(server.url("/")))
    val response = call.execute()
    val source = response.body.source()

	public final fun request ()Lokhttp3/Request;
	public final fun sentRequestAtMillis ()J
	public final fun socket ()Lokio/Socket;
	public fun toString ()Ljava/lang/String;
	public final fun trailers ()Lokhttp3/Headers;
}

public class okhttp3/Response$Builder {
	public fun <init> ()V
	public fun addHeader (Ljava/lang/String;Ljava/lang/String;)Lokhttp3/Response$Builder;