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

package supportapp

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

// Lists the Slack channel configurations for an Amazon Web Services account.
func (c *Client) ListSlackChannelConfigurations(ctx context.Context, params *ListSlackChannelConfigurationsInput, optFns ...func(*Options)) (*ListSlackChannelConfigurationsOutput, error) {
	if params == nil {
		params = &ListSlackChannelConfigurationsInput{}
	}

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

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

type ListSlackChannelConfigurationsInput struct {

	// If the results of a search are large, the API only returns a portion of the
	// results and includes a nextToken pagination token in the response. To retrieve
	// the next batch of results, reissue the search request and include the returned
	// token. When the API returns the last set of results, the response doesn't
	// include a pagination token value.
	NextToken *string

	noSmithyDocumentSerde
}

type ListSlackChannelConfigurationsOutput struct {

	// The configurations for a Slack channel.
	//
	// This member is required.
	SlackChannelConfigurations []types.SlackChannelConfiguration

	// The point where pagination should resume when the response returns only partial
	// results.
	NextToken *string

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

	noSmithyDocumentSerde
}

func (c *Client) addOperationListSlackChannelConfigurationsMiddlewares(st
    
func (c *Client) addOperationListSlackChannelConfigurationsMiddlewares(stack *middleware.Stack, options Options) (err error) {
	if err := stack.Serialize.Add(&setOperationInputMiddleware{}, middleware.After); err != nil {
		return err
	}
	err = stack.Serialize.Add(&awsRestjson1_serializeOpListSlackChannelConfigurations{}, middleware.After)
	if err != nil {
		return err
	}
	err = stack.Deserialize.Add(&awsRestjson1_deserializeOpListSlackChannelConfigurations{}, middleware.After)
	if err != nil {
		return err
	}
	if err := addProtocolFinalizerMiddlewares(stack, options, "ListSlackChannelConfigurations"); 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_opListSlackChannelConfigurations(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
}