getRequestId() method is not able to capture header (issue #123) II

[buzz8year]

public function getRequestId()
{
    if (isset($this->headers['Request-Id'])) {
        return $this->headers['Request-Id'][0];
    }

    return null;
}

• given method is not able to capture header by key 'Request-Id' (reproduction is questionable)
• yet, using lowercased analogue 'request-id' returns expected...
• option:

public function getRequestId()
{
    if (isset($this->headers['Request-Id'])) {
        return $this->headers['Request-Id'][0];
    } else {
        if (isset($this->headers[strtolower('Request-Id')])) {
            return $this->headers[strtolower('Request-Id')][0];
        }
    }

    return null;
}