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[Go] insert code snippets into flows.md (#469)
Create docs-go/flows.md by merging the text with snippets from a valid Go source file. This ensures that the examples in the docs at least compile.
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‎docs-go/flows‎

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# Flows
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Flows are wrapped functions with some additional characteristics over direct
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calls: they are strongly typed, streamable, locally and remotely callable, and
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fully observable.
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Firebase Genkit provides CLI and developer UI tooling for running and debugging flows.
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## Defining flows
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In its simplest form, a flow just wraps a function:
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- {Go}
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%include ../go/internal/doc-snippets/flows.go flow1
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Doing so lets you run the function from the Genkit CLI and developer UI, and is
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a requirement for many of Genkit's features, including deployment and
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observability.
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An important advantage Genkit flows have over directly calling a model API is
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type safety of both inputs and outputs:
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- {Go}
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The argument and result types of a flow can be simple or structured values.
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Genkit will produce JSON schemas for these values using
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[`invopop/jsonschema`](https://pkg.go.dev/github.com/invopop/jsonschema).
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The following flow takes a `string` as input and outputs a `struct`:
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%include ../go/internal/doc-snippets/flows.go msug
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%include ../go/internal/doc-snippets/flows.go flow2
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## Running flows
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To run a flow in your code:
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- {Go}
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%include ../go/internal/doc-snippets/flows.go run1
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You can use the CLI to run flows as well:
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```posix-terminal
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genkit flow:run menuSuggestionFlow '"French"'
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```
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### Streamed
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Here's a simple example of a flow that can stream values:
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- {Go}
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%include ../go/internal/doc-snippets/flows.go streaming-types
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%include ../go/internal/doc-snippets/flows.go streaming
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Note that the streaming callback can be undefined. It's only defined if the
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invoking client is requesting streamed response.
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To invoke a flow in streaming mode:
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- {Go}
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%include ../go/internal/doc-snippets/flows.go invoke-streaming
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If the flow doesn't implement streaming, `StreamFlow()` behaves identically to
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`RunFlow()`.
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You can use the CLI to stream flows as well:
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```posix-terminal
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genkit flow:run menuSuggestionFlow '"French"' -s
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```
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## Deploying flows
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If you want to be able to access your flow over HTTP you will need to deploy it
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first.
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- {Go}
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To deploy flows using Cloud Run and similar services, define your flows, and
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then call `StartFlowServer()`:
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%include ../go/internal/doc-snippets/flows.go main
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`StartFlowsServer` starts a `net/http` server that exposes your flows as HTTP
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endpoints (for example, `http://localhost:3400/menuSuggestionFlow`). Both
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parameters are optional:
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- You can specify the address and port to listen on. If you don't,
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the server listens on any address and the port specified by the PORT
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environment variable; if that is empty, it uses the default of port 3400.
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- You can specify which flows to serve. If you don't, `StartFlowsServer`
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serves all of your defined flows.
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If you want to serve flows on the same host and port as other endpoints, you
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can call `NewFlowServeMux()` to get a handler for your Genkit flows, which you
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can multiplex with your other route handlers:
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%include ../go/internal/doc-snippets/flows.go mux
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## Flow observability
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Sometimes when using 3rd party SDKs that are not instrumented for observability,
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you might want to see them as a separate trace step in the Developer UI. All you
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need to do is wrap the code in the `run` function.
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%include ../go/internal/doc-snippets/flows.go run

‎docs-go/flows.md‎

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<!-- Autogenerated by weave; DO NOT EDIT -->
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13
# Flows
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Flows are wrapped functions with some additional characteristics over direct
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```go
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menuSuggestionFlow := genkit.DefineFlow(
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"menuSuggestionFlow",
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func(ctx context.Context, restaurantTheme string) (string, error) {
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suggestion := makeMenuItemSuggestion(restaurantTheme)
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return suggestion, nil
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},
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)
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"menuSuggestionFlow",
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func(ctx context.Context, restaurantTheme string) (string, error) {
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suggestion := makeMenuItemSuggestion(restaurantTheme)
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return suggestion, nil
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})
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```
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Doing so lets you run the function from the Genkit CLI and developer UI, and is
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```go
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type MenuSuggestion struct {
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ItemName string `json:"item_name"`
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Description string `json:"description"`
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Calories int `json:"calories"`
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ItemName string `json:"item_name"`
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Description string `json:"description"`
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Calories int `json:"calories"`
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}
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```
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```go
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menuSuggestionFlow := genkit.DefineFlow(
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"menuSuggestionFlow",
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func(ctx context.Context, restaurantTheme string) (MenuSuggestion, error) {
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suggestion := makeStructuredMenuItemSuggestion(restaurantTheme)
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return suggestion, nil
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},
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"menuSuggestionFlow",
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func(ctx context.Context, restaurantTheme string) (MenuSuggestion, error) {
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suggestion := makeStructuredMenuItemSuggestion(restaurantTheme)
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return suggestion, nil
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},
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)
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```
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```go
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// Types for illustrative purposes.
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type inputType string
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type outputType string
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type streamType string
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type InputType string
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type OutputType string
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type StreamType string
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```
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menuSuggestionFlow := genkit.DefineFlow(
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"menuSuggestionFlow",
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func(
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ctx context.Context,
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restaurantTheme inputType,
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callback func(context.Context, streamType) error,
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) (outputType, error) {
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var menu strings.Builder
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menuChunks := make(chan streamType)
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go makeFullMenuSuggestion(restaurantTheme, menuChunks)
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for {
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chunk, ok := <-menuChunks
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if !ok {
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break
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}
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if callback != nil {
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callback(context.Background(), chunk)
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}
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menu.WriteString(string(chunk))
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}
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return outputType(menu.String()), nil
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},
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```go
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menuSuggestionFlow := genkit.DefineStreamingFlow(
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"menuSuggestionFlow",
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func(
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ctx context.Context,
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restaurantTheme InputType,
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callback func(context.Context, StreamType) error,
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) (OutputType, error) {
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var menu strings.Builder
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menuChunks := make(chan StreamType)
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go makeFullMenuSuggestion(restaurantTheme, menuChunks)
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for {
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chunk, ok := <-menuChunks
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if !ok {
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break
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}
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if callback != nil {
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callback(context.Background(), chunk)
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}
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menu.WriteString(string(chunk))
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}
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return OutputType(menu.String()), nil
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},
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)
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```
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```go
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genkit.StreamFlow(
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context.Background(),
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menuSuggestionFlow,
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"French",
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)(func(sfv *genkit.StreamFlowValue[outputType, streamType], err error) bool {
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if !sfv.Done {
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fmt.Print(sfv.Output)
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return true
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} else {
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return false
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}
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context.Background(),
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menuSuggestionFlow,
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"French",
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)(func(sfv *genkit.StreamFlowValue[OutputType, StreamType], err error) bool {
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if !sfv.Done {
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fmt.Print(sfv.Output)
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return true
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} else {
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return false
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}
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})
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```
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```go
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func main() {
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genkit.DefineFlow(
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"menuSuggestionFlow",
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func(ctx context.Context, restaurantTheme string) (string, error) {
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// ...
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},
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)
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err := genkit.StartFlowServer(":1234", []string{})
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// startProdServer always returns a non-nil error: the one returned by
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// http.ListenAndServe.
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genkit.DefineFlow(
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"menuSuggestionFlow",
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func(ctx context.Context, restaurantTheme string) (string, error) {
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// ...
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return "", nil
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},
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)
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// StartFlowServer always returns a non-nil error: the one returned by
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// http.ListenAndServe.
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err := genkit.StartFlowServer(":1234", []string{})
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log.Fatal(err)
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}
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```
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```go
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mainMux := http.NewServeMux()
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mainMux.Handle("POST /flow/", http.StripPrefix("/flow/", genkit.NewFlowServeMux()))
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mainMux.Handle("POST /flow/", http.StripPrefix("/flow/", genkit.NewFlowServeMux(nil)))
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```
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## Flow observability
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```go
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genkit.DefineFlow(
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"menuSuggestionFlow",
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func(ctx context.Context, restaurantTheme string) (string, error) {
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themes, err := genkit.Run(ctx, "find-similar-themes", func() (string, error) {
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// ...
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})
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// ...
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},
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)
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"menuSuggestionFlow",
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func(ctx context.Context, restaurantTheme string) (string, error) {
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themes, err := genkit.Run(ctx, "find-similar-themes", func() (string, error) {
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// ...
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return "", nil
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})
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// ...
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return themes, err
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})
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```

‎docs-go/generate.sh‎

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#!/bin/sh -e
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weave=$HOME/go/bin/weave
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if [[ ! -f $weave ]]; then
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echo "installing weave"
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go -C ../go install ./internal/cmd/weave
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fi
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$weave flows > flows.md
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