groovy 双引号字符串（插值）
示例
def param = 'string'
def str = "Double quoted ${param}"
assert str instanceof GString
assert str == 'Double quoted string'默认情况下会急切解析该参数，这意味着适用：
def param = 'string'
def str = "Double quoted ${param}"
param = 'another string'
assert str == 'Double quoted string'为了在每次使用字符串时延迟加载参数，可以这样做：
def param = 'string'
def str = "Double quoted ${ -> param}"
assert str == 'Double quoted string'
param = 'lazy load'
assert str == 'Double quoted lazy load'