Intergrate afero for easier testing (#15)

* Integrate spf13/afero for easier testing

go.mod

@@ -5,6 +5,7 @@ go 1.18
 require (
 	github.com/Masterminds/sprig v2.22.0+incompatible
 	github.com/dave/jennifer v1.5.0
+	github.com/spf13/afero v1.6.0
 	github.com/spf13/cobra v1.4.0
 	github.com/spf13/viper v1.10.1
 	github.com/stoewer/go-strcase v1.2.0
@@ -26,7 +27,6 @@ require (
 	github.com/mitchellh/reflectwalk v1.0.2 // indirect
 	github.com/pelletier/go-toml v1.9.4 // indirect
 	github.com/russross/blackfriday/v2 v2.1.0 // indirect
-	github.com/spf13/afero v1.6.0 // indirect
 	github.com/spf13/cast v1.4.1 // indirect
 	github.com/spf13/jwalterweatherman v1.1.0 // indirect
 	github.com/spf13/pflag v1.0.5 // indirect