Initial commit - learning the basics

using_modules/go.mod

@@ -0,0 +1,3 @@
+module learning.local/using_modules
+
+go 1.24.5

using_modules/using_modules.go

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+package using_modules
+
+import (
+	"fmt"
+	"errors"
+	"math/rand"
+)
+
+// Hello returns a greeting for the named person
+func Hello(name string) (string, error) {
+	// If no name was given, return an error with a message
+	if name == "" {
+		return "", errors.New("empty name")
+	}
+
+	message := fmt.Sprintf(randomFormat(), name)
+	return message, nil
+}
+
+// Hellos retruns a map that associates each of the named people
+// with a greeting message.
+func Hellos(names []string) (map[string]string, error) {
+	// A map to associate names with messages
+	messages := make(map[string]string)
+	// Loop through the received slice of names, calling
+	// the Hello function to get a message for each name.
+	for _, name := range names {
+		message, err := Hello(name)
+		if err != nil {
+			return nil, err
+		}
+		// In the map, associate the terieved message with
+		// the name.
+		messages[name] = message
+	}
+	return messages, nil
+}
+
+
+// randomFormat returns one of a set of greeting messages. The returned
+// message is selected at random.
+
+func randomFormat() string {
+	// A slice of message formats
+	formats := []string{
+		"Hi, %v. Welcome!",
+		"Great to see you, %v!",
+		"Hail, %v! Well met!",
+	}
+
+	// Return a randomly selected message format by specifying
+	// a random index for the slice of formats.
+	return formats[rand.Intn(len(formats))]
+}

using_modules/using_modules_test.go

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+package using_modules
+
+import (
+	"testing"
+	"regexp"
+)
+
+// TestHelloName calls greetings.Hello with a name, checking
+// for a valid return value.
+func TestHelloName(t *testing.T) {
+	name := "Gladys"
+	want := regexp.MustCompile(`\b`+name+`\b`)
+	msg, err := Hello("Gladys")
+	if !want.MatchString(msg) || err != nil {
+		t.Errorf(`Hello("Gladys") = %q, %v, want match for %#q, nill`, msg, err, want)
+	}
+}
+
+// TestHelloEmpty calls greeting.Hello with an empty string,
+// checking for an error
+func TestHelloEmpty(t *testing.T) {
+	msg, err := Hello("")
+	if msg != "" || err == nil {
+		t.Errorf(`Hello("") = %q, %v, want "", error`, msg, err)
+	}
+}