Read the following excerpt from John Keats's "Ode to a Nightingale".Tell about the main idea of the whole poem within 150 words.
O,for a draught of vintage!
that hath beenCool'd a long age in the deep-delved earth,
Tasting of Flora and the country green,Dance,and Provencal song,and sunburnt mirth!
O,for a beaker full of the warm South,
Full of the true,the blushful Hippocrene,
With beaded bubbles winking at the brim,
And purple-stained mouth;
That I might drink,
and leave the world unseen,
And with thee fade away into the forest dim.