Improve handling of JSON Schema in OpenAI API Response Context (#819)

* feat: add jsonschema.Validate and jsonschema.Unmarshal

* fix Sanity check

* remove slices.Contains

* fix Sanity check

* add SchemaWrapper

* update api_integration_test.go

* update method 'reflectSchema' to support 'omitempty' in JSON tag

* add GenerateSchemaForType

* update json_test.go

* update `Warp` to `Wrap`

* fix Sanity check

* fix Sanity check

* update api_internal_test.go

* update README.md

* update README.md

* remove jsonschema.SchemaWrapper

* remove jsonschema.SchemaWrapper

* fix Sanity check

* optimize code formatting

README.md

@@ -743,6 +743,70 @@ func main() {
 }
 ```
 </details>
+
+<details>
+<summary>Structured Outputs</summary>
+
+```go
+package main
+
+import (
+	"context"
+	"fmt"
+	"log"
+
+	"github.com/sashabaranov/go-openai"
+	"github.com/sashabaranov/go-openai/jsonschema"
+)
+
+func main() {
+	client := openai.NewClient("your token")
+	ctx := context.Background()
+
+	type Result struct {
+		Steps []struct {
+			Explanation string `json:"explanation"`
+			Output      string `json:"output"`
+		} `json:"steps"`
+		FinalAnswer string `json:"final_answer"`
+	}
+	var result Result
+	schema, err := jsonschema.GenerateSchemaForType(result)
+	if err != nil {
+		log.Fatalf("GenerateSchemaForType error: %v", err)
+	}
+	resp, err := client.CreateChatCompletion(ctx, openai.ChatCompletionRequest{
+		Model: openai.GPT4oMini,
+		Messages: []openai.ChatCompletionMessage{
+			{
+				Role:    openai.ChatMessageRoleSystem,
+				Content: "You are a helpful math tutor. Guide the user through the solution step by step.",
+			},
+			{
+				Role:    openai.ChatMessageRoleUser,
+				Content: "how can I solve 8x + 7 = -23",
+			},
+		},
+		ResponseFormat: &openai.ChatCompletionResponseFormat{
+			Type: openai.ChatCompletionResponseFormatTypeJSONSchema,
+			JSONSchema: &openai.ChatCompletionResponseFormatJSONSchema{
+				Name:   "math_reasoning",
+				Schema: schema,
+				Strict: true,
+			},
+		},
+	})
+	if err != nil {
+		log.Fatalf("CreateChatCompletion error: %v", err)
+	}
+	err = schema.Unmarshal(resp.Choices[0].Message.Content, &result)
+	if err != nil {
+		log.Fatalf("Unmarshal schema error: %v", err)
+	}
+	fmt.Println(result)
+}
+```
+</details>
 See the `examples/` folder for more.
 
 ## Frequently Asked Questions