How to define Workflow parameters in Go

The first parameter of a Go-based Workflow Definition must be of the workflow.Context type, as it is used by the Temporal Go SDK to pass around Workflow Execution context, and virtually all the Go SDK APIs that are callable from the Workflow require it. It is acquired from the go.temporal.io/sdk/workflow package.

import (
   "go.temporal.io/sdk/workflow"
)

func YourWorkflowDefinition(ctx workflow.Context, param string) error {
 // ...
}

The workflow.Context entity operates similarly to the standard context.Context entity provided by Go. The only difference between workflow.Context and context.Context is that the Done() function, provided by workflow.Context, returns workflow.Channel instead of the standard Go chan.

The second parameter, string, is a custom parameter that is passed to the Workflow when it is invoked. A Workflow Definition may support multiple custom parameters, or none. These parameters can be regular type variables or safe pointers. However, the best practice is to pass a single parameter that is of a struct type, so there can be some backward compatibility if new parameters are added.

type YourWorkflowParam struct {
 WorkflowParamFieldOne string
 WorkflowParamFieldTwo int
}

func YourWorkflowDefinition(ctx workflow.Context, param YourWorkflowParam) error {
 // ...
}

All Workflow Definition parameters must be serializable, regardless of whether pointers or regular type values are used. Parameters can’t be channels, functions, variadic, or unsafe pointers.