fix: set Skew to 1 as default (#42)

README.md

@@ -54,7 +54,7 @@ func Example() {
     // - Algorithm: SHA1
     // - Period: 30
     // - Secret Size: 128
-    // - Skew (time tolerance): 0
+    // - Skew (time tolerance): 1
     // - Digits: 6
     // * Validation result: Passcode is valid
 }

totp/example_test.go

@@ -48,7 +48,7 @@ func Example() {
 	// - Algorithm: SHA1
 	// - Period: 30
 	// - Secret Size: 128
-	// - Skew (time tolerance): 0
+	// - Skew (time tolerance): 1
 	// - Digits: 6
 	// * Validation result: Passcode is valid
 }
@@ -193,7 +193,7 @@ Digits: 8
 Issuer: Example.com
 Period: 30
 Secret Size: 64
-Skew: 0
+Skew: 1
 
 gX7ff3VlT4sCakCjQH69ZQxTbzs=
 -----END TOTP SECRET KEY-----`
@@ -219,7 +219,7 @@ gX7ff3VlT4sCakCjQH69ZQxTbzs=
 	// Issuer: Example.com
 	// Period: 30
 	// Secret Size: 64
-	// Skew: 0
+	// Skew: 1
 	// Secret: QF7N673VMVHYWATKICRUA7V5MUGFG3Z3
 }
 
@@ -332,7 +332,7 @@ func ExampleKey_regenerate() {
 	// Issuer: Example.com
 	// Period: 30
 	// Secret Size: 20
-	// Skew: 0
+	// Skew: 1
 	//
 	// gX7ff3VlT4sCakCjQH69ZQxTbzs=
 	// -----END TOTP SECRET KEY-----
@@ -360,7 +360,7 @@ func ExampleKey_PassCode() {
 	}
 
 	// Validate the passcode with a custom time
-	validationTime := time.Now().Add(-30 * time.Second)
+	validationTime := time.Now().Add(-300 * time.Second)
 
 	if key.ValidateCustom(code, validationTime) {
 		fmt.Println("Passcode is valid with custom time")
@@ -385,8 +385,8 @@ func ExampleKey_PassCodeCustom() {
 
 	timeNow := time.Now()
 
-	// Generate a passcode for a specific time (30 seconds ago)
-	code, err := key.PassCodeCustom(timeNow.Add(-30 * time.Second))
+	// Generate a passcode for a specific time (300 seconds ago)
+	code, err := key.PassCodeCustom(timeNow.Add(-300 * time.Second))
 	if err != nil {
 		log.Fatal(err)
 	}
@@ -400,7 +400,7 @@ func ExampleKey_PassCodeCustom() {
 
 	// To validate a passcode for a specific time, use ValidateCustom()
 	// method.
-	validationTime := timeNow.Add(-30 * time.Second)
+	validationTime := timeNow.Add(-300 * time.Second)
 
 	if key.ValidateCustom(code, validationTime) {
 		fmt.Println("Passcode is valid with custom time")
@@ -437,7 +437,7 @@ func ExampleKey_PEM() {
 	// Issuer: Example.com
 	// Period: 30
 	// Secret Size: 20
-	// Skew: 0
+	// Skew: 1
 	//
 	// gX7ff3VlT4sCakCjQH69ZQxTbzs=
 	// -----END TOTP SECRET KEY-----
@@ -657,7 +657,7 @@ func ExampleOptions() {
 	// Digits: 6
 	// Period: 30
 	// Secret Size: 128
-	// Skew: 0
+	// Skew: 1
 }
 
 // ============================================================================

totp/key_test.go

@@ -301,6 +301,8 @@ func TestKey_PEM(t *testing.T) {
 // Issue #42.
 // If `Period` is set short with `Skew=0`, the passcode validation often fails.
 func TestKey_skew_as_one(t *testing.T) {
+	t.Parallel()
+
 	key, err := GenerateKey("dummy issuer", "dummy account")
 	require.NoError(t, err, "failed to generate TOTP key during test setup")
 
@@ -310,7 +312,7 @@ func TestKey_skew_as_one(t *testing.T) {
 	numIterations := 10
 
 	// If skew is set to 0, the validation fails 60-70% of the time.
-	for i := 0; i < numIterations; i++ {
+	for _ = range numIterations {
 		passCode, err := key.PassCode()
 		require.NoError(t, err, "failed to generate passcode")
 

totp/options.go

@@ -12,7 +12,7 @@ const (
 	OptionDigitsDefault     = Digits(6)         // Google Authenticator does not work other than 6 digits.
 	OptionPeriodDefault     = uint(30)          // 30 seconds is recommended in RFC-6238.
 	OptionSecretSizeDefault = uint(128)         // 128 Bytes.
-	OptionSkewDefault       = uint(0)           // ± Periods. No tolerance.
+	OptionSkewDefault       = uint(1)           // ± 1 period of tolerance.
 )
 
 // ============================================================================
@@ -49,9 +49,10 @@ type Options struct {
 	Period uint
 	// SecretSize is the size of the generated Secret. (Default: 128 bytes)
 	SecretSize uint
-	// Skew is the periods before or after the current time to allow.
+	// Skew is the periods before or after the current time to allow. (Default: 1)
+	//
 	// Value of 1 allows up to Period of either side of the specified time.
-	// Defaults to 0 allowed skews. Values greater than 1 are likely sketchy.
+	// Values greater than 1 are likely sketchy.
 	Skew uint
 }
 
@@ -97,8 +98,7 @@ func (opts *Options) SetDefault() {
 		opts.Digits = OptionDigitsDefault
 	}
 
-	// This is redundant, but it's here to make sure that the default value is
-	// always set.
+	// Fix #42
 	if opts.Skew == 0 {
 		opts.Skew = OptionSkewDefault
 	}