Use type assertion to error out if the type isn't the right one
instead of panic as before this change.
Signed-off-by: Vincent Demeester <vincent@sbr.pm>
It is just an alias type and make the code a little bit more complex
and hard to use from outside `compose` package.
Signed-off-by: Vincent Demeester <vincent@sbr.pm>
Vincent Demeester
Arash Deshmeh
Daniel Nephin