fmt: fix lint issue

* Use unicode.ToUpper func to convert first letter in string to upper case
letter.

* Preallocate memory with correct length and cap because the final
  string is not changing.

function/function.go

@@ -2,7 +2,6 @@
 // Use of this source code is governed by MIT license
 
 // Package function implements some functions for control the function execution and some is for functional programming.
-
 package function
 
 import (
@@ -36,10 +35,10 @@ func Before(n int, fn interface{}) func(args ...interface{}) []reflect.Value {
 		return res
 	}
 }
-
+// Fn is for curry function which is func(...interface{}) interface{}
 type Fn func(...interface{}) interface{}
 
-// Curry make a curryed function
+// Curry make a curry function
 func (f Fn) Curry(i interface{}) func(...interface{}) interface{} {
 	return func(values ...interface{}) interface{} {
 		v := append([]interface{}{i}, values...)

strutil/string.go

@@ -7,6 +7,7 @@ package strutil
 import (
 	"regexp"
 	"strings"
+	"unicode"
 )
 
 // CamelCase covert string to camelCase string.
@@ -40,18 +41,16 @@ func Capitalize(s string) string {
 		return ""
 	}
 
-	res := ""
+	out := make([]rune, len(s))
-	for i, v := range []rune(s) {
+	for i, v := range s {
 		if i == 0 {
-			if v >= 97 && v <= 122 {
+			out[i] = unicode.ToUpper(v)
-				v -= 32
-			}
-			res += string(v)
 		} else {
-			res += strings.ToLower(string(v))
+			out[i] = unicode.ToLower(v)
 		}
 	}
-	return res
+
+	return string(out)
 }
 
 // LowerFirst converts the first character of string to lower case.