You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: api_op_GetIntrospectionSchema.go
    path of file: ./repos/aws-sdk-go-v2/service/appsync
    
    the code of the file until where you have to start completion: // Code generated by smithy-go-codegen DO NOT EDIT.

package appsync

import (
	"context"
	"fmt"
	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
	"github.com/aws/aws-sdk-go-v2/service/appsync/types"
	"github.com/aws/smithy-go/middleware"
	smithyhttp "github.com/aws/smithy-go/transport/http"
)

// Retrieves the introspection schema for a GraphQL API.
func (c *Client) GetIntrospectionSchema(ctx context.Context, params *GetIntrospectionSchemaInput, optFns ...func(*Options)) (*GetIntrospectionSchemaOutput, error) {
	if params == nil {
		params = &GetIntrospectionSchemaInput{}
	}

	result, metadata, err := c.invokeOperation(ctx, "GetIntrospectionSchema", params, optFns, c.addOperationGetIntrospectionSchemaMiddlewares)
	if err != nil {
		return nil, err
	}

	out := result.(*GetIntrospectionSchemaOutput)
	out.ResultMetadata = metadata
	return out, nil
}

type GetIntrospectionSchemaInput struct {

	// The API ID.
	//
	// This member is required.
	ApiId *string

	// The schema format: SDL or JSON.
	//
	// This member is required.
	Format types.OutputType

	// A flag that specifies whether the schema introspection should contain
	// directives.
	IncludeDirectives *bool

	noSmithyDocumentSerde
}

type GetIntrospectionSchemaOutput struct {

	// The schema, in GraphQL Schema Definition Language (SDL) format. For more
	// information, see the GraphQL SDL documentation (http://graphql.org/learn/schema/)
	// .
	Schema []byte

	// Metadata pertaining to the operation's result.
	ResultMetadata middleware.Metadata

	noSmithyDocumentSerde
}

func (c *Client) addOperationGetIntrospectionSchemaMiddlewares(stack *middleware.Stack, options Options) (err error) {
	if err := stack.Serialize.Add(&setOperationInputMiddleware{}, middleware.After); err != nil {
		return err
	}
	err = stack.Serialize.Add(&awsRestjson1_serializeOpGetIntrospectionSchema{}, middleware.After)
	if err != nil {
		return err
	}
	err = stack.Deserialize.Add(&awsRestjson1_deserializeOpGetIntrospectionSchema{}, middleware.After)
	if err != nil {
		return err
	}
	if err 
    
func (c *Client) addOperationGetIntrospectionSchemaMiddlewares(stack *middleware.Stack, options Options) (err error) {
	if err := stack.Serialize.Add(&setOperationInputMiddleware{}, middleware.After); err != nil {
		return err
	}
	err = stack.Serialize.Add(&awsRestjson1_serializeOpGetIntrospectionSchema{}, middleware.After)
	if err != nil {
		return err
	}
	err = stack.Deserialize.Add(&awsRestjson1_deserializeOpGetIntrospectionSchema{}, middleware.After)
	if err != nil {
		return err
	}
	if err := addProtocolFinalizerMiddlewares(stack, options, "GetIntrospectionSchema"); err != nil {
		return fmt.Errorf("add protocol finalizers: %v", err)
	}

	if err = addlegacyEndpointContextSetter(stack, options); err != nil {
		return err
	}
	if err = addSetLoggerMiddleware(stack, options); err != nil {
		return err
	}
	if err = addClientRequestID(stack); err != nil {
		return err
	}
	if err = addComputeContentLength(stack); err != nil {
		return err
	}
	if err = addResolveEndpointMiddleware(stack, options); err != nil {
		return err
	}
	if err = addComputePayloadSHA256(stack); err != nil {
		return err
	}
	if err = addRetry(stack, options); err != nil {
		return err
	}
	if err = addRawResponseToMetadata(stack); err != nil {
		return err
	}
	if err = addRecordResponseTiming(stack); err != nil {
		return err
	}
	if err = addClientUserAgent(stack, options); err != nil {
		return err
	}
	if err = smithyhttp.AddErrorCloseResponseBodyMiddleware(stack); err != nil {
		return err
	}
	if err = smithyhttp.AddCloseResponseBodyMiddleware(stack); err != nil {
		return err
	}
	if err = addSetLegacyContextSigningOptionsMiddleware(stack); err != nil {
		return err
	}
	if err = addOpGetIntrospectionSchemaValidationMiddleware(stack); err != nil {
		return err
	}
	if err = stack.Initialize.Add(newServiceMetadataMiddleware_opGetIntrospectionSchema(options.Region), middleware.Before); err != nil {
		return err
	}
	if err = addRecursionDetection(stack); err != nil {
		return err
	}
	if err = addRequestIDRetrieverMiddleware(stack); err != nil {
		return err
	}
	if err = addResponseErrorMiddleware(stack); err != nil {
		return err
	}
	if err = addRequestResponseLogging(stack, options); err != nil {
		return err
	}
	if err = addDisableHTTPSMiddleware(stack, options); err != nil {
		return err
	}
	return nil
}