Support negotiation wildcards, fix #391 (#1112)

* support negotiation wildcards, fix #391

* fix typo

context.go

@@ -952,7 +952,18 @@ func (c *Context) NegotiateFormat(offered ...string) string {
 	}
 	for _, accepted := range c.Accepted {
 		for _, offert := range offered {
-			if accepted == offert {
+			// According to RFC 2616 and RFC 2396, non-ASCII characters are not allowed in headers,
+			// therefore we can just iterate over the string without casting it into []rune
+			i := 0
+			for ; i < len(accepted); i++ {
+				if accepted[i] == '*' || offert[i] == '*' {
+					return offert
+				}
+				if accepted[i] != offert[i] {
+					break
+				}
+			}
+			if i == len(accepted) {
 				return offert
 			}
 		}