Project harness for Go (#340)

## What was changed
Adds `go/harness/` package, effectively a port of the same Python
harness (`python/harness`).

`go/harness` supports the same harness semantics, structure, and API as
the existing Python harness. The test suite (`project_test.go` and
`worker_test.go`) similarly mimic the existing Python harness test
suite.

The Go worker uniquely supported additional flags for worker deployment
versioning that were not available/used in other languages, that has
correspondingly been added to the Go's worker harness.

**Note**: in contrast to the harness in other languages, the Go harness
is **not** a standalone Go module. There is significant coupling between
the existing go worker code and Omes which would make this either a much
larger change, or cause a lot of duplication. The plan is to use the
existing `workers/go/go.mod` as a single source to manage dependencies
between the harness and the tests that consume it (at least, until this
is resolved)

## Why?
- load testing ergonomics / DX
- Language parity

Author: THardy98

cmd/clioptions/client.go

@@ -111,15 +111,7 @@ func (c *ClientOptions) Dial(metrics *metrics.Metrics, logger *zap.SugaredLogger
 		})
 	}
 
-	dataConverter := converter.NewCompositeDataConverter(
-		converter.NewNilPayloadConverter(),
-		converter.NewByteSlicePayloadConverter(),
-		&PassThroughPayloadConverter{},
-		converter.NewProtoJSONPayloadConverter(),
-		converter.NewProtoPayloadConverter(),
-		converter.NewJSONPayloadConverter(),
-	)
-	clientOptions.DataConverter = dataConverter
+	clientOptions.DataConverter = OmesDataConverter()
 
 	client, err := client.Dial(clientOptions)
 	if err != nil {
@@ -129,6 +121,17 @@ func (c *ClientOptions) Dial(metrics *metrics.Metrics, logger *zap.SugaredLogger
 	return client, nil
 }
 
+func OmesDataConverter() converter.DataConverter {
+	return converter.NewCompositeDataConverter(
+		converter.NewNilPayloadConverter(),
+		converter.NewByteSlicePayloadConverter(),
+		&PassThroughPayloadConverter{},
+		converter.NewProtoJSONPayloadConverter(),
+		converter.NewProtoPayloadConverter(),
+		converter.NewJSONPayloadConverter(),
+	)
+}
+
 // FlagSet adds the relevant flags to populate the options struct and returns a pflag.FlagSet.
 func (c *ClientOptions) FlagSet() *pflag.FlagSet {
 	if c.fs != nil {

cmd/clioptions/worker.go

@@ -19,26 +19,38 @@ type WorkerOptions struct {
 	WorkerActivitiesPerSecond    float64
 	ErrOnUnimplemented           bool
 
-	fs *pflag.FlagSet
+	fs         *pflag.FlagSet
+	usedPrefix string
 }
 
 // FlagSet adds the relevant flags to populate the options struct and returns a pflag.FlagSet.
 func (m *WorkerOptions) FlagSet() *pflag.FlagSet {
+	return m.FlagSetWithPrefix("worker-")
+}
+
+// FlagSetWithPrefix adds worker flags using the provided prefix. The stock
+// OMES CLI keeps the historic "worker-" prefix, while the Go harness mirrors
+// the Python harness worker flags without that prefix.
+func (m *WorkerOptions) FlagSetWithPrefix(prefix string) *pflag.FlagSet {
 	if m.fs != nil {
+		if prefix != m.usedPrefix {
+			panic("prefix mismatch")
+		}
 		return m.fs
 	}
+	m.usedPrefix = prefix
 	m.fs = pflag.NewFlagSet("worker_options", pflag.ExitOnError)
 	m.fs.StringVar(&m.BuildID, "build-id", "", "DEPRECATED: Build ID for legacy Build-ID-based worker versioning. Temporal Server will soon stop supporting the Rules-Based Versioning APIs that back this flag - use --deployment-name and --deployment-build-id instead. Mutually exclusive with --deployment-name")
 	m.fs.StringVar(&m.DeploymentName, "deployment-name", "", "Worker Deployment name. When set, enables Worker Deployment Versioning and must be combined with --deployment-build-id")
 	m.fs.StringVar(&m.DeploymentBuildID, "deployment-build-id", "", "Build ID within the Worker Deployment. Required when --deployment-name is set")
 	m.fs.StringVar(&m.DefaultVersioningBehavior, "default-versioning-behavior", "", "Default versioning behavior for workflows that don't set one at registration. One of: pinned, auto-upgrade. Defaults to auto-upgrade when --deployment-name is set")
-	m.fs.IntVar(&m.MaxConcurrentActivityPollers, "worker-max-concurrent-activity-pollers", 0, "Max concurrent activity pollers")
-	m.fs.IntVar(&m.MaxConcurrentWorkflowPollers, "worker-max-concurrent-workflow-pollers", 0, "Max concurrent workflow pollers")
-	m.fs.IntVar(&m.MaxConcurrentActivities, "worker-max-concurrent-activities", 0, "Max concurrent activities")
-	m.fs.IntVar(&m.MaxConcurrentWorkflowTasks, "worker-max-concurrent-workflow-tasks", 0, "Max concurrent workflow tasks")
-	m.fs.IntVar(&m.ActivityPollerAutoscaleMax, "worker-activity-poller-autoscale-max", 0, "Max for activity poller autoscaling (overrides max-concurrent-activity-pollers")
-	m.fs.IntVar(&m.WorkflowPollerAutoscaleMax, "worker-workflow-poller-autoscale-max", 0, "Max for workflow poller autoscaling (overrides max-concurrent-workflow-pollers")
-	m.fs.Float64Var(&m.WorkerActivitiesPerSecond, "worker-activities-per-second", 0, "Per-worker activity rate limit")
-	m.fs.BoolVar(&m.ErrOnUnimplemented, "worker-err-on-unimplemented", false, "Fail on unimplemented actions (currently this only applies to concurrent client actions)")
+	m.fs.IntVar(&m.MaxConcurrentActivityPollers, prefix+"max-concurrent-activity-pollers", 0, "Max concurrent activity pollers")
+	m.fs.IntVar(&m.MaxConcurrentWorkflowPollers, prefix+"max-concurrent-workflow-pollers", 0, "Max concurrent workflow pollers")
+	m.fs.IntVar(&m.MaxConcurrentActivities, prefix+"max-concurrent-activities", 0, "Max concurrent activities")
+	m.fs.IntVar(&m.MaxConcurrentWorkflowTasks, prefix+"max-concurrent-workflow-tasks", 0, "Max concurrent workflow tasks")
+	m.fs.IntVar(&m.ActivityPollerAutoscaleMax, prefix+"activity-poller-autoscale-max", 0, "Max for activity poller autoscaling (overrides max-concurrent-activity-pollers")
+	m.fs.IntVar(&m.WorkflowPollerAutoscaleMax, prefix+"workflow-poller-autoscale-max", 0, "Max for workflow poller autoscaling (overrides max-concurrent-workflow-pollers")
+	m.fs.Float64Var(&m.WorkerActivitiesPerSecond, prefix+"activities-per-second", 0, "Per-worker activity rate limit")
+	m.fs.BoolVar(&m.ErrOnUnimplemented, prefix+"err-on-unimplemented", false, "Fail on unimplemented actions (currently this only applies to concurrent client actions)")
 	return m.fs
 }

dockerfiles/dotnet.Dockerfile

@@ -28,7 +28,7 @@ COPY loadgen ./loadgen
 COPY scenarios ./scenarios
 COPY metrics ./metrics
 COPY workers/*.go ./workers/
-COPY workers/go/projects/harness/api ./workers/go/projects/harness/api
+COPY workers/go/harness/api ./workers/go/harness/api
 COPY workers/proto/harness ./workers/proto/harness
 COPY go.mod go.sum ./
 

dockerfiles/go.Dockerfile

@@ -10,7 +10,7 @@ COPY loadgen ./loadgen
 COPY scenarios ./scenarios
 COPY metrics ./metrics
 COPY workers/*.go ./workers/
-COPY workers/go/projects/harness/api ./workers/go/projects/harness/api
+COPY workers/go/harness/api ./workers/go/harness/api
 COPY go.mod go.sum ./
 
 # Build the CLI

dockerfiles/java.Dockerfile

@@ -21,7 +21,7 @@ COPY loadgen ./loadgen
 COPY metrics ./metrics
 COPY scenarios ./scenarios
 COPY workers/*.go ./workers/
-COPY workers/go/projects/harness/api ./workers/go/projects/harness/api
+COPY workers/go/harness/api ./workers/go/harness/api
 COPY go.mod go.sum ./
 
 # Build the CLI

dockerfiles/python.Dockerfile

@@ -31,7 +31,7 @@ COPY loadgen ./loadgen
 COPY scenarios ./scenarios
 COPY metrics ./metrics
 COPY workers/*.go ./workers/
-COPY workers/go/projects/harness/api ./workers/go/projects/harness/api
+COPY workers/go/harness/api ./workers/go/harness/api
 COPY go.mod go.sum ./
 
 # Build the CLI

dockerfiles/ruby.Dockerfile

@@ -15,7 +15,7 @@ COPY loadgen ./loadgen
 COPY scenarios ./scenarios
 COPY metrics ./metrics
 COPY workers/*.go ./workers/
-COPY workers/go/projects/harness/api ./workers/go/projects/harness/api
+COPY workers/go/harness/api ./workers/go/harness/api
 COPY go.mod go.sum ./
 
 # Build the CLI

dockerfiles/typescript.Dockerfile

@@ -26,7 +26,7 @@ COPY loadgen ./loadgen
 COPY scenarios ./scenarios
 COPY metrics ./metrics
 COPY workers/*.go ./workers/
-COPY workers/go/projects/harness/api ./workers/go/projects/harness/api
+COPY workers/go/harness/api ./workers/go/harness/api
 COPY go.mod go.sum ./
 
 # Build the CLI

go.mod

@@ -13,7 +13,7 @@ require (
 	github.com/spf13/pflag v1.0.5
 	github.com/stretchr/testify v1.11.1
 	github.com/temporalio/features v0.0.0-20260331150122-757294c2a9e9
-	github.com/temporalio/omes/workers/go/projects/harness/api v0.0.0-00010101000000-000000000000
+	github.com/temporalio/omes/workers/go/harness/api v0.0.0-00010101000000-000000000000
 	go.temporal.io/api v1.62.7
 	go.temporal.io/sdk v1.42.0
 	go.uber.org/zap v1.27.0
@@ -71,5 +71,5 @@ require (
 replace (
 	github.com/temporalio/features/features => github.com/temporalio/features/features v0.0.0-20260324215619-e5868d9ba03f
 	github.com/temporalio/features/harness/go => github.com/temporalio/features/harness/go v0.0.0-20260324215619-e5868d9ba03f
-	github.com/temporalio/omes/workers/go/projects/harness/api => ./workers/go/projects/harness/api
+	github.com/temporalio/omes/workers/go/harness/api => ./workers/go/harness/api
 )

scenarios/project/handle.go

@@ -7,7 +7,7 @@ import (
 	"time"
 
 	"github.com/temporalio/omes/loadgen"
-	api "github.com/temporalio/omes/workers/go/projects/harness/api"
+	api "github.com/temporalio/omes/workers/go/harness/api"
 	"google.golang.org/grpc"
 	"google.golang.org/grpc/credentials/insecure"
 )