first commit

createAGoModule/greetings/go.mod

@@ -0,0 +1,3 @@
+module example.com/greetings
+
+go 1.17

createAGoModule/greetings/greetings.go

@@ -0,0 +1,59 @@
+package greetings
+
+import (
+	"errors"
+	"fmt"
+    "math/rand"
+    "time"
+)
+
+// 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 name, errors.New("empty name")
+    }
+    // Create a message using a random format.
+    message := fmt.Sprintf(randomFormat(), name)
+//    message := fmt.Sprintf(randomFormat())
+    return message, nil
+}
+
+// Hellos returns 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 retrieved message with
+        // the name.
+        messages[name] = message
+    }
+    return messages, nil
+}
+
+// init sets initial values for variables used in the function.
+func init() {
+    rand.Seed(time.Now().UnixNano())
+}
+
+// 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))]
+}

createAGoModule/greetings/greetings_test.go

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+package greetings
+
+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.Fatalf(`Hello("Gladys") = %q, %v, want match for %#q, nil`, msg, err, want)
+    }
+}
+
+// TestHelloEmpty calls greetings.Hello with an empty string,
+// checking for an error.
+func TestHelloEmpty(t *testing.T) {
+    msg, err := Hello("")
+    if msg != "" || err == nil {
+        t.Fatalf(`Hello("") = %q, %v, want "", error`, msg, err)
+    }
+}