Putting object to Spaces with Access Key gives cert error

I get this error

x509: certificate signed by unknown authority

when I try to put an object to Spaces using access keys in a docker container. I can get files just fine, and I can put files from my local machine (not in a docker container). I’m using the minio package from a golang app. This happens even with ssl=false. Is it looking for a cert only on puts?

Here’s what my code looks like

	endpoint := "sfo3.digitaloceanspaces.com"
	bucket := "mybucket"
	ssl := false
	client, err := minio.New(endpoint, accessKey, secKey, ssl)
	if err != nil {
		fmt.Println(err)
		return nil
	}
	//this get works fine
	obj, err := client.GetObject(bucket, fileName, minio.GetObjectOptions{})
	if err != nil {
		fmt.Println(err)
		return nil
	}
	reader := bytes.NewReader(contents)
	//this put fails
	_, err = client.PutObject(bucket, "test.jpeg", reader, reader.Size(), minio.PutObjectOptions{})
	if err != nil {
		fmt.Println(err)	//this is where I get the error
	}