Cancel and timeout contexts are handled correctly.

lib/myipio/myipio.go

@@ -8,7 +8,6 @@ import (
 	"io"
 	"net"
 	"net/http"
-	"net/url"
 	"strings"
 )
 
@@ -34,61 +33,61 @@ var (
 	ErrNoIPv4    = errors.New("ip address is not ipv4")
 	ErrInvalid   = errors.New("ip address is invalid")
 	ErrStatus    = errors.New("unusual my-ip.io server response")
-)
 
-const (
-	domain = "api4.my-ip.io"
-	link   = "https://api4.my-ip.io/ip.json"
+	link = "https://api4.my-ip.io/ip.json"
 )
 
+const domain = "api4.my-ip.io"
+
 // IPv4 returns the Internet facing IP address of the free my-ip.io service.
 func IPv4(ctx context.Context, cancel context.CancelFunc) (string, error) {
-	s, err := request(ctx, cancel, link)
+	r, err := request(ctx, cancel, link)
+	if err == nil && ctx.Err() == context.Canceled {
+		return "", nil
+	}
 	if err != nil {
-		if _, ok := err.(*url.Error); ok {
-			if strings.Contains(err.Error(), "context deadline exceeded") {
-				fmt.Printf("\n%s: timeout\n", domain)
-				return "", nil
-			}
-			fmt.Printf("\n%s: %s\n", domain, err)
+		switch errors.Unwrap(err) {
+		case context.DeadlineExceeded:
+			fmt.Printf("\n%s: timeout\n", domain)
 			return "", nil
+		default:
+			return "", fmt.Errorf("%s error: %s", domain, err)
 		}
-		return "", fmt.Errorf("%s error: %s", domain, err)
 	}
 
-	return s, nil
+	if ok, err := r.valid(); !ok {
+		return r.IP, err
+	}
+
+	return r.IP, nil
 }
 
-func request(ctx context.Context, cancel context.CancelFunc, url string) (string, error) {
+func request(ctx context.Context, cancel context.CancelFunc, url string) (Result, error) {
 	defer cancel()
 
 	req, err := http.NewRequestWithContext(ctx, http.MethodGet, url, nil)
 	if err != nil {
-		return "", err
+		return Result{}, err
 	}
 
 	resp, err := http.DefaultClient.Do(req)
 	if err != nil {
-		return "", err
+		return Result{}, err
 	}
 	defer resp.Body.Close()
 
 	//log.Printf("\nReceived %d from %s\n", resp.StatusCode, url)
 
 	if resp.StatusCode != http.StatusOK {
-		return "", fmt.Errorf("%s, %w", strings.ToLower(resp.Status), ErrStatus)
+		return Result{}, fmt.Errorf("%s, %w", strings.ToLower(resp.Status), ErrStatus)
 	}
 
 	r, err := parse(resp.Body)
 	if err != nil {
-		return "", err
-	}
-
-	if ok, err := r.valid(); !ok {
-		return r.IP, err
+		return Result{}, err
 	}
 
-	return r.IP, nil
+	return r, nil
 }
 
 func parse(r io.Reader) (Result, error) {

lib/myipio/myipio_test.go

@@ -19,13 +19,31 @@ func BenchmarkRequest(b *testing.B) {
 	fmt.Println(s)
 }
 
-func TestIPv4(t *testing.T) {
-	rc, rto := context.WithTimeout(context.Background(), 5*time.Second)
-	wantS, _ := request(rc, rto, link)
+func TestTimeout(t *testing.T) {
+	ctx, timeout := context.WithTimeout(context.Background(), 0*time.Second)
+	if _, err := IPv4(ctx, timeout); !errors.Is(err, nil) {
+		t.Errorf("IPv4() = %v, want %v", err, nil)
+	}
+}
 
-	ctx, timeout := context.WithTimeout(context.Background(), 5*time.Second)
-	if gotS, _ := IPv4(ctx, timeout); gotS != wantS {
-		t.Errorf("IPv4() = %v, want %v", gotS, wantS)
+func TestCancel(t *testing.T) {
+	ctx, cancel := context.WithCancel(context.Background())
+	cancel()
+	want := context.Canceled
+	_, err := IPv4(ctx, cancel)
+	if err == nil {
+		t.Errorf("IPv4() error = %v, want error string", err)
+	}
+	if !errors.Is(ctx.Err(), want) {
+		t.Errorf("IPv4() context.error = %v, want %v", err, want)
+	}
+}
+
+func TestError(t *testing.T) {
+	link = "invalid url"
+	ctx, timeout := context.WithTimeout(context.Background(), 30*time.Second)
+	if _, err := IPv4(ctx, timeout); errors.Is(err, nil) {
+		t.Errorf("IPv4() = %v, want an error", err)
 	}
 }
 
@@ -38,8 +56,8 @@ func Test_request(t *testing.T) {
 	}{
 		{"empty", "", false, "unsupported protocol scheme"},
 		{"html", "https://example.com", false, "invalid character"},
-		{"404", link + "/abcdef", false, "404 not found"},
-		{"okay", link, true, ""},
+		{"404", "https://api4.my-ip.io/ip.json/abcdef", false, "404 not found"},
+		{"okay", "https://api4.my-ip.io/ip.json", true, ""},
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
@@ -48,7 +66,7 @@ func Test_request(t *testing.T) {
 			if err != nil && tt.wantErr != "" && !strings.Contains(fmt.Sprint(err), tt.wantErr) {
 				t.Errorf("get() error = %v, want %v", err, tt.wantErr)
 			}
-			if bool(gotS != "") != tt.isValid {
+			if bool(gotS.IP != "") != tt.isValid {
 				t.Errorf("get() = %v, want an ip addr: %v", gotS, tt.isValid)
 			}
 		})