Consider increasing cyclomatic complexity

The following discussion from !161 (merged) should be addressed:

• @andrewn started a discussion: (+1 comment)

  @nolith I've had to do a whole lot of refactoring in app.go's Run method to get around the cyclometric complexity requirement.

  Aside: breaking the build on a cyclometric complexity of 10 feels too low for Golang - effectively each function is limited to 5 methods having an error check, but that discussion can be had elsewhere.

/cc @nick.thomas