call.execute().use { response ->
      val source = response.body.source()
      assertThat(response.header("h1")).isEqualTo("v1")
      assertThat(source.readUtf8(5)).isEqualTo("Hello")
      call.cancelLater(500.milliseconds)
      val trailersDelay =
        measureTime {
          val exception =
            assertFailsWith<IOException> {
              response.trailers()
            }