add more documentation, examples with tests to illustrate reusable components

publicsuffix/examples_test.go

@@ -0,0 +1,18 @@
+package publicsuffix_test
+
+import (
+	"context"
+	"fmt"
+
+	"golang.org/x/exp/slog"
+
+	"github.com/mjl-/mox/dns"
+	"github.com/mjl-/mox/publicsuffix"
+)
+
+func ExampleLookup() {
+	// Lookup the organizational domain for sub.example.org.
+	orgDom := publicsuffix.Lookup(context.Background(), slog.Default(), dns.Domain{ASCII: "sub.example.org"})
+	fmt.Println(orgDom)
+	// Output: example.org
+}