What is the right way to conditionally assign multiple properties to a struct

I'm working on a resolver function for a GraphQL query for a BE I'm writing in Go. In the resolver, I have user data that I want to update, using an input value containing several possible update properties.

In JavaScript, this can be done quickly through destructuring (pseudo):

const mergedObj = {...oldProps, ...newProps}

For now, my resolver function looks like this (using gqlgen for GraphQL Go resolvers):

func (r *mutationResolver) ModifyUser(ctx context.Context, input *model.ModifyUserInput) (*model.User, error) {
	id := input.ID
	us, ok := r.Resolver.UserStore[id]
	if !ok {
		return nil, fmt.Errorf("not found")
	}

	if input.FirstName != nil {
		us.FirstName = *input.FirstName
	}

	if input.LastName != nil {
		us.LastName = *input.LastName
	}

	if input.ProfileImage != nil {
		us.ProfileImage = input.ProfileImage
	}

	if input.Password != nil {
		us.Password = *input.Password
	}

	if input.Email != nil {
		us.Email = *input.Email
	}

	if input.InTomorrow != nil {
		us.InTomorrow = input.InTomorrow
	}

	if input.DefaultDaysIn != nil {
		us.DefaultDaysIn = input.DefaultDaysIn
	}

	r.Resolver.UserStore[id] = us

	return &us, nil
}

This feels quite boilerplatey. Would it make sense in this situation to iterate through struct keys? Or is there another pattern I'm missing?

Use a function to reduce the boilerplate:

func mergef[T any](a, b *T) {
	if b != nil {
		*a = *b
	}
}

...
mergef(&us.FirstName, input.FirstName)
mergef(&us.LastName, input.LastName)
...

Use the reflect package to reduce more boilerplate:

// merge sets fields in struct pointed to by d to 
// dereferenced fields in struct pointed to by s. 
//
// Argument s must point to a struct with pointer type
// fields.   
// Argument d must point to a struct with fields that 
// correspond to the fields in s: there must be a field
// in d with the same name as a field in s; the type of
// the field in s must be a pointer to the type of the field
// in d.   
func merge(d, s any) {
	sv := reflect.ValueOf(s).Elem()
	dv := reflect.ValueOf(d).Elem()
	for i := 0; i < sv.NumField(); i++ {
		sf := sv.Field(i)
		if sf.IsNil() {
			continue
		}
		df := dv.FieldByName(sv.Type().Field(i).Name)
		df.Set(sf.Elem())
	}
}

Employ the function like this:

merge(us, input)