test: add examples for random package

random/random.go

@@ -19,7 +19,8 @@ const (
 	LETTERS       = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"
 )
 
-// RandInt generate random int between min and max, maybe min,  not be max
+// RandInt generate random int between min and max, maybe min,  not be max.
+// Play: https://go.dev/play/p/pXyyAAI5YxD
 func RandInt(min, max int) int {
 	if min == max {
 		return min
@@ -28,10 +29,12 @@ func RandInt(min, max int) int {
 		min, max = max, min
 	}
 	r := rand.New(rand.NewSource(time.Now().UnixNano()))
+
 	return r.Intn(max-min) + min
 }
 
-// RandBytes generate random byte slice
+// RandBytes generate random byte slice.
+// Play: https://go.dev/play/p/EkiLESeXf8d
 func RandBytes(length int) []byte {
 	if length < 1 {
 		return []byte{}
@@ -41,45 +44,54 @@ func RandBytes(length int) []byte {
 	if _, err := io.ReadFull(crand.Reader, b); err != nil {
 		return nil
 	}
+
 	return b
 }
 
-// RandString generate random string
+// RandString generate random string of specified length.
+// Play: https://go.dev/play/p/W2xvRUXA7Mi
 func RandString(length int) string {
 	return random(LETTERS, length)
 }
 
-// RandUpper generate a random upper case string
+// RandUpper generate a random upper case string.
+// Play: https://go.dev/play/p/29QfOh0DVuh
 func RandUpper(length int) string {
 	return random(UPPER_LETTERS, length)
 }
 
-// RandLower generate a random lower case string
+// RandLower generate a random lower case string.
+// Play: https://go.dev/play/p/XJtZ471cmtI
 func RandLower(length int) string {
 	return random(LOWER_LETTERS, length)
 }
 
-// RandNumeral generate a random numeral string
+// RandNumeral generate a random numeral string of specified length.
+// Play: https://go.dev/play/p/g4JWVpHsJcf
 func RandNumeral(length int) string {
 	return random(NUMERAL, length)
 }
 
-// RandNumeralOrLetter generate a random numeral or letter string
+// RandNumeralOrLetter generate a random numeral or letter string.
+// Play: https://go.dev/play/p/19CEQvpx2jD
 func RandNumeralOrLetter(length int) string {
 	return random(NUMERAL+LETTERS, length)
 }
 
-// random generate a random string based on given string range
+// random generate a random string based on given string range.
 func random(s string, length int) string {
 	b := make([]byte, length)
 	r := rand.New(rand.NewSource(time.Now().UnixNano()))
+
 	for i := range b {
 		b[i] = s[r.Int63()%int64(len(s))]
 	}
+
 	return string(b)
 }
 
-// UUIdV4 generate a random UUID of version 4 according to RFC 4122
+// UUIdV4 generate a random UUID of version 4 according to RFC 4122.
+// Play: https://go.dev/play/p/_Z9SFmr28ft
 func UUIdV4() (string, error) {
 	uuid := make([]byte, 16)