feat attachment filename support utf8 (#3071)

context.go

@@ -6,7 +6,6 @@ package gin
 
 import (
 	"errors"
-	"fmt"
 	"io"
 	"io/ioutil"
 	"log"
@@ -1018,7 +1017,11 @@ func (c *Context) FileFromFS(filepath string, fs http.FileSystem) {
 // FileAttachment writes the specified file into the body stream in an efficient way
 // On the client side, the file will typically be downloaded with the given filename
 func (c *Context) FileAttachment(filepath, filename string) {
-	c.Writer.Header().Set("Content-Disposition", fmt.Sprintf("attachment; filename=\"%s\"", filename))
+	if isASCII(filename) {
+		c.Writer.Header().Set("Content-Disposition", `attachment; filename="`+filename+`"`)
+	} else {
+		c.Writer.Header().Set("Content-Disposition", `attachment; filename*=UTF-8''`+url.QueryEscape(filename))
+	}
 	http.ServeFile(c.Writer, c.Request, filepath)
 }