Flow continuation fails when combining fdk handler to accept http input to function

[fnproject]

Flow continuation fails when combining fdk handler to accept http input to function

[gviedma-zz]

There are a couple of reasons your example is failing:

1. The complete flow-based program needs to be enclosed within a flows.WithFlow block. If you consume input or produce function output outside the block, things will break.
2. By calling printResult you are writing to the function's output. However, you later try to serialize a struct as json to stdout as well, so you have a mix of logging output and json. I doubt that is what you want.

Here is a snippet which does what I believe you want and works:

func myHandler(ctx context.Context, in io.Reader, out io.Writer) {
	flows.WithFlow(
		func() {
			p := &Person{Name: "World"}
			json.NewDecoder(in).Decode(p)
                        // use the name passed in as input to the function as initial flow stage
			cf := flows.CurrentFlow().CompletedValue(p.Name)
			valueCh, errorCh := cf.ThenApply(strings.ToUpper).ThenApply(strings.ToLower).Get()
			select {
			case value := <-valueCh:
                                // output the result of the flow transformation as the result of this function
				p.Name = value.(string)
				json.NewEncoder(out).Encode(p)
			case err := <-errorCh:
				io.WriteString(out, fmt.Sprintf(`{"error":"Flow failed with error %v}`, err))
			case <-time.After(time.Minute * 1):
				io.WriteString(out, `{"error":"Flow timed out}`)
			}
		})
}