feat: better structured internal

internal/config/source.go

@@ -0,0 +1,29 @@
+package config
+
+import (
+	"io"
+	"os"
+)
+
+// Defines the consumption of different types of input sources.
+type Source interface {
+	// Get the data.
+	Pull() (string, error)
+}
+
+// A source coming from a string.
+type StringSource struct{ data string }
+
+func (this StringSource) Pull() (string, error) { return this.data, nil }
+
+// A source coming from standard input.
+type StdinSource struct{}
+
+func (this StdinSource) Pull() (string, error) {
+	data, err := io.ReadAll(os.Stdin)
+	if err != nil {
+		return "", err
+	}
+
+	return string(data), nil
+}