Gin1.5 bytes.Buffer to strings.Builder (#1939)

* Replace bytes.Buffer to strings.Builder

* Merge the latest changes

* Update errors.go

debug.go

@@ -5,7 +5,6 @@
 package gin
 
 import (
-	"bytes"
 	"fmt"
 	"html/template"
 	"runtime"
@@ -38,7 +37,7 @@ func debugPrintRoute(httpMethod, absolutePath string, handlers HandlersChain) {
 
 func debugPrintLoadTemplate(tmpl *template.Template) {
 	if IsDebugging() {
-		var buf bytes.Buffer
+		var buf strings.Builder
 		for _, tmpl := range tmpl.Templates() {
 			buf.WriteString("\t- ")
 			buf.WriteString(tmpl.Name())

errors.go

@@ -5,9 +5,9 @@
 package gin
 
 import (
-	"bytes"
 	"fmt"
 	"reflect"
+	"strings"
 
 	"github.com/gin-gonic/gin/internal/json"
 )
@@ -158,7 +158,7 @@ func (a errorMsgs) String() string {
 	if len(a) == 0 {
 		return ""
 	}
-	var buffer bytes.Buffer
+	var buffer strings.Builder
 	for i, msg := range a {
 		fmt.Fprintf(&buffer, "Error #%02d: %s\n", i+1, msg.Err)
 		if msg.Meta != nil {