Configure base path at runtime

## Feature Request

Allow prefix to be configured at runtime. This is because in many setups prefix is part of runtime configurations as person building the app and deploying it are two different people.

For example if you ship RPM, DEB or docker containers you ship already built binaries and expect user to pass argument to the application (or config file) rather than rebuild the app.

## Implement Suggestion

I think the simplest way would be a context that router could read.