float32(0.49999999)      // 0.5 of type float32
float64(-1e-1000)        // 0.0 of type float64
string('x')              // "x" of type string
string(0x266c)           // "♬" of type string
myString("foo" + "bar")  // "foobar" of type myString
string([]byte{'a'})      // not a constant: []byte{'a'} is not a constant
(*int)(nil)              // not a constant: nil is not a constant, *int is not a boolean, numeric, or string type

    String CRAWLER_DOCUMENT_HTML_CANONICAL_XPATH = "crawler.document.html.canonical.xpath";

    /** The key of the configuration. e.g. noscript,script,style,header,footer,aside,nav,a[rel=nofollow] */
    String CRAWLER_DOCUMENT_HTML_PRUNED_TAGS = "crawler.document.html.pruned.tags";

    /** The key of the configuration. e.g. 120 */