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_AssociatePackage.go
    path of file: ./repos/aws-sdk-go-v2/service/opensearch
    
    the code of the file until where you have to start completion: // Code generated by smithy-go-codegen DO NOT EDIT.

package opensearch

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

// Associates a package with an Amazon OpenSearch Service domain. For more
// information, see Custom packages for Amazon OpenSearch Service (https://docs.aws.amazon.com/opensearch-service/latest/developerguide/custom-packages.html)
// .
func (c *Client) AssociatePackage(ctx context.Context, params *AssociatePackageInput, optFns ...func(*Options)) (*AssociatePackageOutput, error) {
	if params == nil {
		params = &AssociatePackageInput{}
	}

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

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

// Container for the request parameters to the AssociatePackage operation.
type AssociatePackageInput struct {

	// Name of the domain to associate the package with.
	//
	// This member is required.
	DomainName *string

	// Internal ID of the package to associate with a domain. Use DescribePackages to
	// find this value.
	//
	// This member is required.
	PackageID *string

	noSmithyDocumentSerde
}

// Container for the response returned by the AssociatePackage operation.
type AssociatePackageOutput struct {

	// Information about a package that is associated with a domain.
	DomainPackageDetails *types.DomainPackageDetails

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

	noSmithyDocumentSerde
}

func (c *Client) addOperationAssociatePackageMiddlewares(stack *middleware.Stack, options Options) (err error) {
	if err := stack.Serialize.Add(&setOperationInputMiddleware{}, middleware.After); err != nil {
		return err
	}
	err = stack.Serialize.Add(&awsRestjson1_serializeOpAssociatePackage{}, middleware.After)
	if err != nil {
		return err
	}
	err = stack.Deserialize.Add(&awsRestjson1_deserializeOpAssociatePa
    
func (c *Client) addOperationAssociatePackageMiddlewares(stack *middleware.Stack, options Options) (err error) {
	if err := stack.Serialize.Add(&setOperationInputMiddleware{}, middleware.After); err != nil {
		return err
	}
	err = stack.Serialize.Add(&awsRestjson1_serializeOpAssociatePackage{}, middleware.After)
	if err != nil {
		return err
	}
	err = stack.Deserialize.Add(&awsRestjson1_deserializeOpAssociatePackage{}, middleware.After)
	if err != nil {
		return err
	}
	if err := addProtocolFinalizerMiddlewares(stack, options, "AssociatePackage"); 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 = addOpAssociatePackageValidationMiddleware(stack); err != nil {
		return err
	}
	if err = stack.Initialize.Add(newServiceMetadataMiddleware_opAssociatePackage(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
}