First, the address ach Gott is not part of the sentence. This can easily be seen from the following examples, where an address has been prepended to the major sentence types of German.
Hans, hast du einen Augenblick Zeit? (yes-no question)
Hans, wann hast du denn Zeit? (wh-question)
Hans, ich wollte dich etwas fragen. (declarative sentence)
Second, although the imperative is commonly taught, at least to beginners, to have the verb in first position, German actually allows the verb to be in second position in imperatives as well.
Komm jetzt her! (V1)
Jetzt komm her! (V2)
Sieh' being the imperative of sehen and ach Gott being an address, the sentence in question is an ordinary imperative with the verb in second position.