docs: add Go example for interactive weather assistant in Step 5 (#318)

* docs: add Go example for interactive weather assistant in Step 5

* fix: address review feedback for Go Step 5 example

* fix: simplify condition in session event handling for Go example

Author: Ota1022

docs/getting-started.md

@@ -786,6 +786,113 @@ python weather_assistant.py
 
 </details>
 
+<details>
+<summary><strong>Go</strong></summary>
+
+Create `weather-assistant.go`:
+
+```go
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"log"
+	"math/rand"
+	"os"
+	"strings"
+
+	copilot "github.com/github/copilot-sdk/go"
+)
+
+type WeatherParams struct {
+	City string `json:"city" jsonschema:"The city name"`
+}
+
+type WeatherResult struct {
+	City        string `json:"city"`
+	Temperature string `json:"temperature"`
+	Condition   string `json:"condition"`
+}
+
+func main() {
+	getWeather := copilot.DefineTool(
+		"get_weather",
+		"Get the current weather for a city",
+		func(params WeatherParams, inv copilot.ToolInvocation) (WeatherResult, error) {
+			conditions := []string{"sunny", "cloudy", "rainy", "partly cloudy"}
+			temp := rand.Intn(30) + 50
+			condition := conditions[rand.Intn(len(conditions))]
+			return WeatherResult{
+				City:        params.City,
+				Temperature: fmt.Sprintf("%d°F", temp),
+				Condition:   condition,
+			}, nil
+		},
+	)
+
+	client := copilot.NewClient(nil)
+	if err := client.Start(); err != nil {
+		log.Fatal(err)
+	}
+	defer client.Stop()
+
+	session, err := client.CreateSession(&copilot.SessionConfig{
+		Model:     "gpt-4.1",
+		Streaming: true,
+		Tools:     []copilot.Tool{getWeather},
+	})
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	session.On(func(event copilot.SessionEvent) {
+		if event.Type == "assistant.message_delta" {
+			if event.Data.DeltaContent != nil {
+				fmt.Print(*event.Data.DeltaContent)
+			}
+		}
+		if event.Type == "session.idle" {
+			fmt.Println()
+		}
+	})
+
+	fmt.Println("🌤️  Weather Assistant (type 'exit' to quit)")
+	fmt.Println("   Try: 'What's the weather in Paris?' or 'Compare weather in NYC and LA'\n")
+
+	scanner := bufio.NewScanner(os.Stdin)
+	for {
+		fmt.Print("You: ")
+		if !scanner.Scan() {
+			break
+		}
+		input := scanner.Text()
+		if strings.ToLower(input) == "exit" {
+			break
+		}
+
+		fmt.Print("Assistant: ")
+		_, err = session.SendAndWait(copilot.MessageOptions{Prompt: input}, 0)
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "Error: %v\n", err)
+			break
+		}
+		fmt.Println()
+	}
+	if err := scanner.Err(); err != nil {
+		fmt.Fprintf(os.Stderr, "Input error: %v\n", err)
+	}
+}
+```
+
+Run with:
+
+```bash
+go run weather-assistant.go
+```
+
+</details>
+
 <details>
 <summary><strong>.NET</strong></summary>