src/Leevel/Http/Response.php
public function setEtag(string $etag): IResponse
    {
        if ($this->checkFlowControl()) {
            return $this;
        }

        $this->setHeader('Etag', $etag);

        return $this;
    }
public function setEtag(string $etag): IResponse
    {
        if ($this->checkFlowControl()) {
            return $this;
        }

        $this->setHeader('Etag', $etag);

        return $this;
    }
设置自定义标识符.

@param string $etag

@return $this