雙引號字串（插值）

def param = 'string'
def str = "Double quoted ${param}"
assert str instanceof GString
assert str == 'Double quoted string'

預設情況下，該引數是急切解決的，這意味著這適用：

def param = 'string'
def str = "Double quoted ${param}"
param = 'another string'
assert str == 'Double quoted string'

為了在每次使用字串時懶惰地載入引數，可以這樣做：

def param = 'string'
def str = "Double quoted ${ -> param}"
assert str == 'Double quoted string'
param = 'lazy load'
assert str == 'Double quoted lazy load'