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_DescribeReservedInstanceOfferings.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"
)

// Describes the available Amazon OpenSearch Service Reserved Instance offerings
// for a given Region. For more information, see Reserved Instances in Amazon
// OpenSearch Service (https://docs.aws.amazon.com/opensearch-service/latest/developerguide/ri.html)
// .
func (c *Client) DescribeReservedInstanceOfferings(ctx context.Context, params *DescribeReservedInstanceOfferingsInput, optFns ...func(*Options)) (*DescribeReservedInstanceOfferingsOutput, error) {
	if params == nil {
		params = &DescribeReservedInstanceOfferingsInput{}
	}

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

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

// Container for the request parameters to a DescribeReservedInstanceOfferings
// operation.
type DescribeReservedInstanceOfferingsInput struct {

	// An optional parameter that specifies the maximum number of results to return.
	// You can use nextToken to get the next page of results.
	MaxResults int32

	// If your initial DescribeReservedInstanceOfferings operation returns a nextToken
	// , you can include the returned nextToken in subsequent
	// DescribeReservedInstanceOfferings operations, which returns results in the next
	// page.
	NextToken *string

	// The Reserved Instance identifier filter value. Use this parameter to show only
	// the available instance types that match the specified reservation identifier.
	ReservedInstanceOfferingId *string

	noSmithyDoc
    
func (c *Client) addOperationDescribeReservedInstanceOfferingsMiddlewares(stack *middleware.Stack, options Options) (err error) {
	if err := stack.Serialize.Add(&setOperationInputMiddleware{}, middleware.After); err != nil {
		return err
	}
	err = stack.Serialize.Add(&awsRestjson1_serializeOpDescribeReservedInstanceOfferings{}, middleware.After)
	if err != nil {
		return err
	}
	err = stack.Deserialize.Add(&awsRestjson1_deserializeOpDescribeReservedInstanceOfferings{}, middleware.After)
	if err != nil {
		return err
	}
	if err := addProtocolFinalizerMiddlewares(stack, options, "DescribeReservedInstanceOfferings"); 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 = stack.Initialize.Add(newServiceMetadataMiddleware_opDescribeReservedInstanceOfferings(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
}