diff --git a/go/ai/generator.go b/go/ai/generator.go
index 032221789..f066910fa 100644
--- a/go/ai/generator.go
+++ b/go/ai/generator.go
@@ -16,7 +16,9 @@ package ai
 
 import (
 	"context"
+	"errors"
 	"fmt"
+	"strings"
 
 	"github.com/google/genkit/go/genkit"
 )
@@ -61,3 +63,28 @@ type generatorAction struct {
 func (ga *generatorAction) Generate(ctx context.Context, input *GenerateRequest, cb genkit.NoStream) (*GenerateResponse, error) {
 	return ga.action.Run(ctx, input, cb)
 }
+
+// Text returns the contents of the first candidate in a
+// [GenerateResponse] as a string. It returns an error if there
+// are no candidates or if the candidate has no message.
+func (gr *GenerateResponse) Text() (string, error) {
+	if len(gr.Candidates) == 0 {
+		return "", errors.New("no candidates returned")
+	}
+	msg := gr.Candidates[0].Message
+	if msg == nil {
+		return "", errors.New("candidate with no message")
+	}
+	if len(msg.Content) == 0 {
+		return "", errors.New("candidate message has no content")
+	}
+	if len(msg.Content) == 1 {
+		return msg.Content[0].Text(), nil
+	} else {
+		var sb strings.Builder
+		for _, p := range msg.Content {
+			sb.WriteString(p.Text())
+		}
+		return sb.String(), nil
+	}
+}
diff --git a/go/genkit/dotprompt/genkit.go b/go/genkit/dotprompt/genkit.go
index 3b20ba4ac..ee5a7ad8c 100644
--- a/go/genkit/dotprompt/genkit.go
+++ b/go/genkit/dotprompt/genkit.go
@@ -17,6 +17,8 @@ package dotprompt
 import (
 	"context"
 	"errors"
+	"reflect"
+	"strings"
 
 	"github.com/google/genkit/go/ai"
 	"github.com/google/genkit/go/genkit"
@@ -37,6 +39,54 @@ type ActionInput struct {
 	Model string `json:"model,omitempty"`
 }
 
+// BuildVariables returns a map for [ActionInput.Variables] based
+// on a pointer to a struct value. The struct value should have
+// JSON tags that correspond to the Prompt's input schema.
+// Only exported fields of the struct will be used.
+func (p *Prompt) BuildVariables(input any) (map[string]any, error) {
+	v := reflect.ValueOf(input).Elem()
+	if v.Kind() != reflect.Struct {
+		return nil, errors.New("BuildVariables: not a pointer to a struct")
+	}
+	vt := v.Type()
+
+	// TODO(ianlancetaylor): Verify the struct with p.Frontmatter.Schema.
+
+	m := make(map[string]any)
+
+fieldLoop:
+	for i := 0; i < vt.NumField(); i++ {
+		ft := vt.Field(i)
+		if ft.PkgPath != "" {
+			continue
+		}
+
+		jsonTag := ft.Tag.Get("json")
+		jsonName, rest, _ := strings.Cut(jsonTag, ",")
+		if jsonName == "" {
+			jsonName = ft.Name
+		}
+
+		vf := v.Field(i)
+
+		// If the field is the zero value, and omitempty is set,
+		// don't pass it as a prompt input variable.
+		if vf.IsZero() {
+			for rest != "" {
+				var key string
+				key, rest, _ = strings.Cut(rest, ",")
+				if key == "omitempty" {
+					continue fieldLoop
+				}
+			}
+		}
+
+		m[jsonName] = vf.Interface()
+	}
+
+	return m, nil
+}
+
 // buildRequest prepares an [ai.GenerateRequest] based on the prompt,
 // using the input variables and other information in the [ActionInput].
 func (p *Prompt) buildRequest(input *ActionInput) (*ai.GenerateRequest, error) {
diff --git a/go/samples/coffee-shop/main.go b/go/samples/coffee-shop/main.go
new file mode 100644
index 000000000..87d3a2d88
--- /dev/null
+++ b/go/samples/coffee-shop/main.go
@@ -0,0 +1,192 @@
+// Copyright 2024 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// This program can be manually tested like so:
+// Start the server listening on port 3100:
+//
+//	go run . &
+//
+// Tell it to run an action:
+//
+//	curl -d '{"key":"/flow/testAllCoffeeFlows/testAllCoffeeFlows", "input":{"start": {"input":null}}}'  http://localhost:3100/api/runAction
+package main
+
+import (
+	"context"
+	"fmt"
+	"log"
+	"os"
+
+	"github.com/google/genkit/go/ai"
+	"github.com/google/genkit/go/genkit"
+	"github.com/google/genkit/go/genkit/dotprompt"
+	"github.com/google/genkit/go/plugins/googleai"
+	"github.com/invopop/jsonschema"
+)
+
+const simpleGreetingPromptTemplate = `
+You're a barista at a nice coffee shop.
+A regular customer named {{customerName}} enters.
+Greet the customer in one sentence, and recommend a coffee drink.
+`
+
+type simpleGreetingInput struct {
+	CustomerName string `json:"customerName"`
+}
+
+const greetingWithHistoryPromptTemplate = `
+{{role "user"}}
+Hi, my name is {{customerName}}. The time is {{currentTime}}. Who are you?
+
+{{role "model"}}
+I am Barb, a barista at this nice underwater-themed coffee shop called Krabby Kooffee.
+I know pretty much everything there is to know about coffee,
+and I can cheerfully recommend delicious coffee drinks to you based on whatever you like.
+
+{{role "user"}}
+Great. Last time I had {{previousOrder}}.
+I want you to greet me in one sentence, and recommend a drink.
+`
+
+type customerTimeAndHistoryInput struct {
+	CustomerName  string `json:"customerName"`
+	CurrentTime   string `json:"currentTime"`
+	PreviousOrder string `json:"previousOrder"`
+}
+
+type testAllCoffeeFlowsOutput struct {
+	Pass    bool   `json:"pass"`
+	Replies []string `json:"replies,omitempty"`
+	Error   string `json:"error,omitempty"`
+}
+
+func main() {
+	apiKey := os.Getenv("GEMINI_API_KEY")
+	if apiKey == "" {
+		fmt.Fprintln(os.Stderr, "coffee-shop example requires setting GEMINI_API_KEY in the environment.")
+		fmt.Fprintln(os.Stderr, "You can get an API key at https://ai.google.dev.")
+		os.Exit(1)
+	}
+
+	if err := googleai.Init(context.Background(), "gemini-pro", apiKey); err != nil {
+		log.Fatal(err)
+	}
+
+	simpleGreetingPrompt, err := dotprompt.Define("simpleGreeting",
+		&dotprompt.Frontmatter{
+			Name: "simpleGreeting",
+			Model: "google-genai",
+			Input: dotprompt.FrontmatterInput{
+				Schema: jsonschema.Reflect(simpleGreetingInput{}),
+			},
+			Output: &ai.GenerateRequestOutput{
+				Format: ai.OutputFormatText,
+			},
+		},
+		simpleGreetingPromptTemplate,
+		nil,
+	)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	simpleGreetingFlow := genkit.DefineFlow("simpleGreeting", func(ctx context.Context, input *simpleGreetingInput, _ genkit.NoStream) (string, error) {
+		vars, err := simpleGreetingPrompt.BuildVariables(input)
+		if err != nil {
+			return "", err
+		}
+		ai := &dotprompt.ActionInput{ Variables: vars }
+		resp, err := simpleGreetingPrompt.Execute(ctx, ai)
+		if err != nil {
+			return "", err
+		}
+		text, err := resp.Text()
+		if err != nil {
+			return "", fmt.Errorf("simpleGreeting: %v", err)
+		}
+		return text, nil
+	})
+
+	greetingWithHistoryPrompt, err := dotprompt.Define("greetingWithHistory",
+		&dotprompt.Frontmatter{
+			Name: "greetingWithHistory",
+			Model: "google-genai",
+			Input: dotprompt.FrontmatterInput{
+				Schema: jsonschema.Reflect(customerTimeAndHistoryInput{}),
+			},
+			Output: &ai.GenerateRequestOutput{
+				Format: ai.OutputFormatText,
+			},
+		},
+		greetingWithHistoryPromptTemplate,
+		nil,
+	)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	greetingWithHistoryFlow := genkit.DefineFlow("greetingWithHistory", func(ctx context.Context, input *customerTimeAndHistoryInput, _ genkit.NoStream) (string, error) {
+		vars, err := greetingWithHistoryPrompt.BuildVariables(input)
+		if err != nil {
+			return "", err
+		}
+		ai := &dotprompt.ActionInput{ Variables: vars }
+		resp, err := greetingWithHistoryPrompt.Execute(ctx, ai)
+		if err != nil {
+			return "", err
+		}
+		text, err := resp.Text()
+		if err != nil {
+			return "", fmt.Errorf("greetingWithHistory: %v", err)
+		}
+		return text, nil
+	})
+
+	genkit.DefineFlow("testAllCoffeeFlows", func(ctx context.Context, _ struct{}, _ genkit.NoStream) (*testAllCoffeeFlowsOutput, error) {
+		test1, err := genkit.RunFlow(ctx, simpleGreetingFlow, &simpleGreetingInput{
+			CustomerName: "Sam",
+		})
+		if err != nil {
+			out := &testAllCoffeeFlowsOutput{
+				Pass:  false,
+				Error: err.Error(),
+			}
+			return out, nil
+		}
+		test2, err := genkit.RunFlow(ctx, greetingWithHistoryFlow, &customerTimeAndHistoryInput{
+			CustomerName:  "Sam",
+			CurrentTime:   "09:45am",
+			PreviousOrder: "Caramel Macchiato",
+		})
+		if err != nil {
+			out := &testAllCoffeeFlowsOutput{
+				Pass:  false,
+				Error: err.Error(),
+			}
+			return out, nil
+		}
+		out := &testAllCoffeeFlowsOutput{
+			Pass:    true,
+			Replies: []string{
+				test1,
+				test2,
+			},
+		}
+		return out, nil
+	})
+
+	if err := genkit.StartDevServer(""); err != nil {
+		log.Fatal(err)
+	}
+}