https://github.com/grpc/grpc-go/issues/1229#issuecomment-302755717 DoWithTimeout runs f and returns its error.

Return the base directory (with the trailing /) for the base path.

Normalize the base path.

Ensure public URL start and ends with /.

Join all parts of the URL to make sure that there is only a single / between them regardless of if they have leading or trailing /.