Lots of code cleanup, better error handling, etc...

internal/pkg/errors/errors.go

@@ -0,0 +1,20 @@
+package errors
+
+
+type error interface {
+	Error() string
+}
+
+// errorString is a trivial implementation of error.
+type errorString struct {
+	s string
+}
+
+func (e *errorString) Error() string {
+	return e.s
+}
+
+// New returns an error that formats as the given text.
+func New(text string) error {
+	return &errorString{text}
+}