Did refactoring; shell_test.

Signed-off-by: Kouhei Maeda <mkouhei@palmtb.net>
Fixed goImports() fail.

Signed-off-by: Kouhei Maeda <mkouhei@palmtb.net>
Added unit test of the case of goimports fail.

Signed-off-by: Kouhei Maeda <mkouhei@palmtb.net>