otlp grpc exporter support

[windmeup]

go-zero/core/trace/agent.go

Line 56 in 79de932

// Just support jaeger and zipkin now, more for later

Is there a kindGrpc support plan? The current implements is not work, becasue the unstarted exporter never start:

go-zero/core/trace/agent.go

Lines 62 to 67 in 79de932

	case kindGrpc:
	return otlptracegrpc.NewUnstarted(
	otlptracegrpc.WithInsecure(),
	otlptracegrpc.WithEndpoint(c.Endpoint),
	otlptracegrpc.WithDialOption(grpc.WithBlock()),
	), nil