File Upload multipart/form-data validation issue

[MarcSky]

Good afternoon. Need your help.
I am using openapi: 3.0.0 and github.com/oapi-codegen/nethttp-middleware v1.0.2 library for data validation.
I am trying to upload a photo file to the server but I am facing the following problem.

request body has an error: failed to decode request body: path attachment: unsupported content type \"image/png\”
My swagger file looks like this

  openapi: 3.0.0

  /files/upload:
    post:
      summary: Uploads document
      operationId: uploadFile
      tags:
        - files
      requestBody:
        required: true
        content:
          multipart/form-data:
            schema:
              type: object
              properties:
                attachment:
                  type: string
                  format: binary
              required:
                - attachment
            encoding:
              attachment:
                contentType: image/png, image/jpeg
      responses:
        "200":
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/FileUploadResponse'

I suspect the error occurs github.com/getkin/kin-openapi/openapi3filter/req_resp_decoder.go on line 1462.
we send image contentType = image/png to contentType = multipart/form-data for validation and get an error.

		var value any
		if _, value, err = decodeBody(part, http.Header(part.Header), valueSchema, subEncFn); err != nil {
			if v, ok := err.(*ParseError); ok {
				return nil, &ParseError{path: []any{name}, Cause: v}
			}
			return nil, fmt.Errorf(“part %s: %w”, name, err)
		}

at this point we expect contentType = multipart/form-data but get another one contentType = image/png and return with an error.

	decoder, ok := bodyDecoders[mediaType]
	if !ok {
		return "", nil, &ParseError{
			Kind:   KindUnsupportedFormat,
			Reason: fmt.Sprintf("%s %q", prefixUnsupportedCT, mediaType),
		}
	}

to solve this problem you need to put inside bodyDecoders not only contentType=multipart/form-data but also all contentType and encoding lists (image/png, image/jpeg and so on) in bodyDecoders.