accept 0x(0X) start in 'hexadecimal' tag (#620)

* accept hexadecimal which starts with 0x(0X) optionally

regexes.go

@@ -9,7 +9,7 @@ const (
 	alphaUnicodeNumericRegexString   = "^[\\p{L}\\p{N}]+$"
 	numericRegexString               = "^[-+]?[0-9]+(?:\\.[0-9]+)?$"
 	numberRegexString                = "^[0-9]+$"
-	hexadecimalRegexString           = "^[0-9a-fA-F]+$"
+	hexadecimalRegexString           = "^(0[xX])?[0-9a-fA-F]+$"
 	hexcolorRegexString              = "^#(?:[0-9a-fA-F]{3}|[0-9a-fA-F]{6})$"
 	rgbRegexString                   = "^rgb\\(\\s*(?:(?:0|[1-9]\\d?|1\\d\\d?|2[0-4]\\d|25[0-5])\\s*,\\s*(?:0|[1-9]\\d?|1\\d\\d?|2[0-4]\\d|25[0-5])\\s*,\\s*(?:0|[1-9]\\d?|1\\d\\d?|2[0-4]\\d|25[0-5])|(?:0|[1-9]\\d?|1\\d\\d?|2[0-4]\\d|25[0-5])%\\s*,\\s*(?:0|[1-9]\\d?|1\\d\\d?|2[0-4]\\d|25[0-5])%\\s*,\\s*(?:0|[1-9]\\d?|1\\d\\d?|2[0-4]\\d|25[0-5])%)\\s*\\)$"
 	rgbaRegexString                  = "^rgba\\(\\s*(?:(?:0|[1-9]\\d?|1\\d\\d?|2[0-4]\\d|25[0-5])\\s*,\\s*(?:0|[1-9]\\d?|1\\d\\d?|2[0-4]\\d|25[0-5])\\s*,\\s*(?:0|[1-9]\\d?|1\\d\\d?|2[0-4]\\d|25[0-5])|(?:0|[1-9]\\d?|1\\d\\d?|2[0-4]\\d|25[0-5])%\\s*,\\s*(?:0|[1-9]\\d?|1\\d\\d?|2[0-4]\\d|25[0-5])%\\s*,\\s*(?:0|[1-9]\\d?|1\\d\\d?|2[0-4]\\d|25[0-5])%)\\s*,\\s*(?:(?:0.[1-9]*)|[01])\\s*\\)$"
@@ -36,7 +36,7 @@ const (
 	latitudeRegexString              = "^[-+]?([1-8]?\\d(\\.\\d+)?|90(\\.0+)?)$"
 	longitudeRegexString             = "^[-+]?(180(\\.0+)?|((1[0-7]\\d)|([1-9]?\\d))(\\.\\d+)?)$"
 	sSNRegexString                   = `^[0-9]{3}[ -]?(0[1-9]|[1-9][0-9])[ -]?([1-9][0-9]{3}|[0-9][1-9][0-9]{2}|[0-9]{2}[1-9][0-9]|[0-9]{3}[1-9])$`
-  hostnameRegexStringRFC952        = `^[a-zA-Z]([a-zA-Z0-9\-]+[\.]?)*[a-zA-Z0-9]$`                                                                      // https://tools.ietf.org/html/rfc952
+	hostnameRegexStringRFC952        = `^[a-zA-Z]([a-zA-Z0-9\-]+[\.]?)*[a-zA-Z0-9]$`                                                                      // https://tools.ietf.org/html/rfc952
 	hostnameRegexStringRFC1123       = `^([a-zA-Z0-9]{1}[a-zA-Z0-9_-]{0,62}){1}(\.[a-zA-Z0-9_]{1}[a-zA-Z0-9_-]{0,62})*?$`                                 // accepts hostname starting with a digit https://tools.ietf.org/html/rfc1123
 	fqdnRegexStringRFC1123           = `^([a-zA-Z0-9]{1}[a-zA-Z0-9_-]{0,62})(\.[a-zA-Z0-9_]{1}[a-zA-Z0-9_-]{0,62})*?(\.[a-zA-Z]{1}[a-zA-Z0-9]{0,62})\.?$` // same as hostnameRegexStringRFC1123 but must contain a non numerical TLD (possibly ending with '.')
 	btcAddressRegexString            = `^[13][a-km-zA-HJ-NP-Z1-9]{25,34}$`                                                                                // bitcoin address

validator_test.go

@@ -7765,6 +7765,14 @@ func TestHexadecimal(t *testing.T) {
 	errs := validate.Var(s, "hexadecimal")
 	Equal(t, errs, nil)
 
+	s = "0xff0044"
+	errs = validate.Var(s, "hexadecimal")
+	Equal(t, errs, nil)
+
+	s = "0Xff0044"
+	errs = validate.Var(s, "hexadecimal")
+	Equal(t, errs, nil)
+
 	s = "abcdefg"
 	errs = validate.Var(s, "hexadecimal")
 	NotEqual(t, errs, nil)