reflect: add example for FieldByName

Change-Id: I47e1cc261fdcd6f83a8593893b979d130150d0b2
Reviewed-on: https://go-review.googlesource.com/c/go/+/407174
Auto-Submit: Ian Lance Taylor <iant@google.com>
Run-TryBot: Ian Lance Taylor <iant@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Michael Knyszek <mknyszek@google.com>

src/reflect/example_test.go

@@ -194,3 +194,16 @@ func ExampleValue_FieldByIndex() {
 	// Output:
 	// embedded last name: Embedded Doe
 }
+
+func ExampleValue_FieldByName() {
+	type user struct {
+		firstName string
+		lastName  string
+	}
+	u := user{firstName: "John", lastName: "Doe"}
+	s := reflect.ValueOf(u)
+
+	fmt.Println("Name:", s.FieldByName("firstName"))
+	// Output:
+	// Name: John
+}