public static function updateMetadata($metadata, $jwtAuthUri)
    {
        $context = Tracer::spanContext();
        if ($context->enabled()) {
            $propagator = new GrpcMetadataPropagator();
            $metadata += [
                $propagator->key() => [$propagator->formatter()->serialize($context)]
            ];
        }
        return $metadata;
    }
public static function updateMetadata($metadata, $jwtAuthUri)
    {
        $context = Tracer::spanContext();
        if ($context->enabled()) {
            $propagator = new GrpcMetadataPropagator();
            $metadata += [
                $propagator->key() => [$propagator->formatter()->serialize($context)]
            ];
        }
        return $metadata;
    }
public static function updateMetadata ( $ metadata , $ jwtAuthUri ) { $ context = Tracer :: spanContext ( ) ; if ( $ context -> enabled ( ) ) { $ propagator = new GrpcMetadataPropagator ( ) ; $ metadata += [ $ propagator -> key ( ) => [ $ propagator -> formatter ( ) -> serialize ( $ context ) ] ] ; } return $ metadata ; }
Update metadata handler for grpc clients.

Example:

```
use OpenCensus\Trace\Integrations\Grpc;

# MathClient is the generated client from the proto definition
$client = new Math\MathClient($host, ['update_metadata' => [Grpc::class, 'updateMetadata']]);

# The call will pass the current trace context using the GrpcMetadataPropagator and BinaryFormatter
$call = $client->Div($divArgs);
$response = $call->wait();
```

@param array $metadata
@param string $jwtAuthUri
@return array
Update metadata handler for grpc clients .