Start workflow with JSON input using HTTP API

[anhtqweb]

I'm trying to start a workflow using HTTP API according to the Cadence HTTP API documentation. It's working as expected when I do not define input for the workflow. When I changed the workflow definition to have input like below:

func MyWorkflow(ctx cadence.Context, input MyInput) error {
    ...
}

type MyInput struct {
    SomeString: string,
    SomeInteger: int
} 

and send a HTTP POST request to start the workflow with the data like below:

{
  "domain": "sample-domain",
  "workflow_id": "sample-workflow-id",
  "execution_start_to_close_timeout": "61s",
  "task_start_to_close_timeout": "60s",
  "workflow_type": {
    "name": "sample-workflow-type"
  },
  "task_list": {
    "name": "sample-task-list"
  },
  "identity": "client-name-visible-in-history",
  "request_id": "8049B932-6C2F-415A-9BB2-241DCF4CFC9C",
  "input": {
    "SomeString": "blah",
    "SomeInteger": 123
  }
}

The workflow failed immediately and gave out this error:

{
  "reason": "cadenceInternal:Generic",
  "details": "unable to decode the workflow function input bytes with error: unable to decode argument: 0, *MyInput, with json error: EOF, function name: sample-workflow-type",
...
}

Can someone help me point out where I did wrong? Thanks a lot!