No need match all c.allowedHeaders every time

[yyonghe]

No need match all c.allowedHeaders every time.

[rs]

Please add context, you comment does not seem to match what your change is doing.

[yyonghe]

In function areHeadersAllowed(), when checking headers, if we've matched, we can break the for loop.

func (c *Cors) areHeadersAllowed(requestedHeaders []string) bool {
	if c.allowedHeadersAll || len(requestedHeaders) == 0 {
		return true
	}
	for _, header := range requestedHeaders {
		header = http.CanonicalHeaderKey(header)
		found := false
		for _, h := range c.allowedHeaders {
			if h == header {
				found = true
				break // added this line
			}
		}
		if !found {
			return false
		}
	}
	return true
}