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

package iam

import (
	"context"
	"errors"
	"fmt"
	awsmiddleware "github.com/aws/aws-sdk-go-v2/aws/middleware"
	"github.com/aws/aws-sdk-go-v2/service/iam/types"
	smithy "github.com/aws/smithy-go"
	"github.com/aws/smithy-go/middleware"
	smithytime "github.com/aws/smithy-go/time"
	smithyhttp "github.com/aws/smithy-go/transport/http"
	smithywaiter "github.com/aws/smithy-go/waiter"
	"time"
)

// Retrieves information about the specified IAM user, including the user's
// creation date, path, unique ID, and ARN. If you do not specify a user name, IAM
// determines the user name implicitly based on the Amazon Web Services access key
// ID used to sign the request to this operation.
func (c *Client) GetUser(ctx context.Context, params *GetUserInput, optFns ...func(*Options)) (*GetUserOutput, error) {
	if params == nil {
		params =
    
func (w *UserExistsWaiter) WaitForOutput(ctx context.Context, params *GetUserInput, maxWaitDur time.Duration, optFns ...func(*UserExistsWaiterOptions)) (*GetUserOutput, error) {
	if maxWaitDur <= 0 {
		return nil, fmt.Errorf("maximum wait time for waiter must be greater than zero")
	}

	options := w.options
	for _, fn := range optFns {
		fn(&options)
	}

	if options.MaxDelay <= 0 {
		options.MaxDelay = 120 * time.Second
	}

	if options.MinDelay > options.MaxDelay {
		return nil, fmt.Errorf("minimum waiter delay %v must be lesser than or equal to maximum waiter delay of %v.", options.MinDelay, options.MaxDelay)
	}

	ctx, cancelFn := context.WithTimeout(ctx, maxWaitDur)
	defer cancelFn()

	logger := smithywaiter.Logger{}
	remainingTime := maxWaitDur

	var attempt int64
	for {

		attempt++
		apiOptions := options.APIOptions
		start := time.Now()

		if options.LogWaitAttempts {
			logger.Attempt = attempt
			apiOptions = append([]func(*middleware.Stack) error{}, options.APIOptions...)
			apiOptions = append(apiOptions, logger.AddLogger)
		}

		out, err := w.client.GetUser(ctx, params, func(o *Options) {
			o.APIOptions = append(o.APIOptions, apiOptions...)
			for _, opt := range options.ClientOptions {
				opt(o)
			}
		})

		retryable, err := options.Retryable(ctx, params, out, err)
		if err != nil {
			return nil, err
		}
		if !retryable {
			return out, nil
		}

		remainingTime -= time.Since(start)
		if remainingTime < options.MinDelay || remainingTime <= 0 {
			break
		}

		// compute exponential backoff between waiter retries
		delay, err := smithywaiter.ComputeDelay(
			attempt, options.MinDelay, options.MaxDelay, remainingTime,
		)
		if err != nil {
			return nil, fmt.Errorf("error computing waiter delay, %w", err)
		}

		remainingTime -= delay
		// sleep for the delay amount before invoking a request
		if err := smithytime.SleepWithContext(ctx, delay); err != nil {
			return nil, fmt.Errorf("request cancelled while waiting, %w", err)
		}
	}
	return nil, fmt.Errorf("exceeded max wait time for UserExists waiter")
}