@Nullable
    public static HttpHeaders get(RequestContext ctx) {
        return InternalGrpcWebTrailers.get(ctx);
    }
Returns the gRPC-Web trailers which was set to the specified {@link RequestContext} using
{@link #set(RequestContext, HttpHeaders)}.

<p>A gRPC-Web response does not contain a separated trailers according to the
<a href="https://github.com/grpc/grpc/blob/master/doc/PROTOCOL-WEB.md#protocol-differences-vs-grpc-over-http2">
gRPC-Web spec</a>:
<ul>
  <li>Trailers must be the last message of the response.</li>
  <li>Trailers may be sent together with response headers, with no message in the body.</li>
</ul>
That means the response trailers should be pulled out from {@link AggregatedHttpResponse#headers()}}
or parsed from {@link AggregatedHttpResponse#content()}.

<p>This method is useful when {@link RetryRuleWithContent} needs {@link GrpcHeaderNames#GRPC_STATUS}
to decide whether to retry. For example:
<pre>{@code
GrpcClients.builder(grpcServerUri)
           .decorator(RetryingClient.newDecorator(
                   RetryRuleWithContent.onResponse((ctx, response) -> {
                       // Note that we should aggregate the response to get the trailers.
                       return response.aggregate().thenApply(aggregated -> {
                           HttpHeaders trailers = GrpcWebTrailers.get(ctx);
                           // Retry if the 'grpc-status' is not equal to 0.
                           return trailers != null && trailers.getInt(GrpcHeaderNames.GRPC_STATUS) != 0;
                       });
                   })))
           .build(MyGrpcStub.class);
}</pre>
grpc/src/main/java/com/linecorp/armeria/common/grpc/GrpcWebTrailers.java