Modern straight flute has no G key, and the back of the flute body is marked with the meaning of "Germany".
If it is the kind of high-pitched flute about 30cm used in ordinary primary and secondary schools in the mainland, it should be played in C major according to the fingering marked on the fingering table attached when buying the flute.
If you have any questions, please come to clarinet to discuss O(∩_∩)O~